Here are some things you should know about the TestFlight build of Hyperspace:

• The current TestFlight build WILL NOT ACTUALLY RECLAIM DISK SPACE - For now, this feature is disabled in TestFlight. The user interface will tell you that it has reclaimed disk space, but it’s not true. What it will do is everything except the very last step in the reclamation process, where it replaces the existing file with a space-saving clone. So please do test the “Reclaim Space” feature. Despite the fact that it will stop just short of actually reclaiming space, it will do all the earlier steps, which are important to test.

• TestFlight builds will not actually charge you any money - Please do test the “purchase” flow, but rest assured that you will not be charged any actual money when using a TestFlight build.

• TestFlight uses an accelerated subscription renewal rate - For TestFlight builds, each subscription is renewed daily, up to 6 times within a one-week period, regardless of the subscription’s actual duration. Note that this only applies to auto-renewing subscriptions (I think…), so the one-time, non-renewing “subscriptions” will expire in real time (unless I figure out a way to manually delete or reset them…)

• You can send feedback from within the TestFlight app on macOS - Launch the TestFlight app itself (not the TestFlight build of Hyperspace), click on Hyperspace in the sidebar, then click the “Send Feedback” button.

  You can also send feedback by emailing hyperspace@hypercritical.co

• The icon is a placeholder - The final icon is still in the works.

A: Hyperspace searches for files with identical content within one or more folders. If it finds any, it can then reclaim the disk space taken by all but one of the identical files—without removing any of the files!

You can learn more about how this is done, if you’re interested, but the short version is that Hyperspace uses a standard feature of the macOS file system. The Finder does the same thing when it duplicates a file.

A: The following words and phrases will be used in this document and throughout the Hyperspace user interface:

• Scanning: The process of examining files to determine if they are candidates for reclamation.
• Reclamation: The process of replacing a set of files that have identical content with space-saving clones of each other, reclaiming disk space.
• Space-saving clones: Files that all share a single instance of data on disk. See a longer explanation of how this works, if you’re interested.
• Disk - The physical device where data is stored. In years past, this might have been a spinning hard disk. These days, it’s more likely to be an SSD. The term “disk space” is mostly a holdover from years past when hard disks were more common. Today we might say “storage space” instead. Much of the text in this document and in the Hyperspace app itself still uses the term “disk space,” mostly because the term is still in common use—and because the app’s creator was born in the 1970s.

There are three steps to using Hyperspace: Scan, Review, and Reclaim.

Scan

After launching Hyperspace, click the “Choose Folder…” button at the top of the main window, then select a folder to scan. This should be a folder that you own. Folders owned by other users or by the system can be scanned, but only files owned by the current user can be reclaimed.

Once a folder is selected, a green “+" and a red “-” button will appear beside it. Click the “-” button to unselect the folder. Click the “+" button to add another folder. When more than one folder is selected, Hyperspace will search for duplicates within both folders. Selecting multiple folders offers some new possibilities, described in another section of this document.

After selecting one or more folders, click the “Scan” button in the main window to start the scan. Hyperspace will search the entire contents of the folder, including all sub-folders, looking for files that have identical contents. Hyperspace will only consider files that meet the criteria configured in its Settings and that are not excluded for safety reasons.

During the scan, Hyperspace will report any errors it encounters. You can view these errors by clicking the “View” button that will appear next to the “Scan Errors” label in the main window. The kinds of scan errors are explained in another part of this document.

When the scan is complete, the number of files eligible for reclamation will be shown next to the “Eligible Files” label in the main window. If no eligible files were found, consider choosing a different folder, choosing an additional folder, or adjusting the Settings to make more files eligible, and scan again.

Review

If some eligible files were found, then click the “Review Files” button. This will open the Review Window. The purpose of the Review Window is to give you a chance to see all the identical files that were found, and to optionally decide which of those files should be replaced with space-saving clones. By default, all the files are selected.

The Review Window lists all the groups of identical files, each represented by a designated “Source” file. Each group of identical files has a checkbox next to it. Unchecking that checkbox excludes all the files in the group from the reclamation process.

Click on a file group to see its contents expanded in the detail view at the bottom of the Review Window. There you can uncheck the checkbox next to individual files to exclude them from the reclamation process. You can also designate a new “Source” file by Control-clicking or right-clicking on a file in the detail view and selecting the “Make Source” item from the context menu.

As you make changes, the “Selected Savings” header at the top of the window shows the running total of the space that will be reclaimed based on which files are included and excluded.

When you’re done reviewing the list of files, click the “Done” button and return to the main window.

Reclaim

Now it’s finally time to reclaim some space. Click the “Reclaim Space” button to start the reclamation process. Hyperspace will replace all the eligible, selected files with space-saving clones. When the reclamation completes, the total amount of space reclaimed will be shown. You can also see your lifetime space savings by selecting “About Hyperspace” from the “Hyperspace” menu in the menu bar.

During reclamation, Hyperspace will report any errors it encounters. You can view these errors by clicking the “View” button that will appear next to the “Reclamation Errors” label in the main window. The kinds of reclamation errors are explained in another part of this document.

Certain kinds of errors will immediately stop the reclamation process. These are errors that cause the contents of the disk to be left in an inconsistent state, usually by “stranding” a file that Hyperspace was unable to clean up. As soon as a single file is stranded, the reclamation process stops. The “Reclamation Errors” window will show these kinds of errors in orange or red text, and each error of this kind will include clean-up instructions and a clickable link to reveal the stranded file in the Finder. You should manually clean up these files by either renaming them back to their original names or by deleting them, depending on what kind of operation failed, according to the error message.

Hyperspace is free to download on the Mac App Store. Once downloaded, it’s free to scan an unlimited number of files. Scanning will let you know how much space is eligible to be reclaimed. If you decide you want to reclaim that space, initiating the reclamation process will prompt you to pay for Hyperspace.

Two kinds of purchases are possible: one-time purchases and subscriptions.

One-time purchases are exactly as described: a payment that is made one time and is never automatically charged again. A one-time purchase may unlock the app for one month or one year or forever, but it will never “renew”, and that charge will not be repeated.

Subscriptions will automatically renew according to a schedule, and each renewal will incur an additional payment equal to the price of the subscription. To stop a subscription from renewing, cancel it. Subscription management can also be accessed from within Hyperspace’s Settings window by clicking the “Manage Subscription” button.

Only Apple can issue refunds for apps sold through the Mac App Store. Developers do not have the ability to issue refunds. You can request a refund at Apple’s website.

Apple also provides some more information about billing and subscriptions.

Though most files can be scanned, not every scanned file can be reclaimed. In addition to the limitations configured in Hyperspace’s Settings and the safety measures built into the app, a file must meet all the following criteria in order to be successfully reclaimed:

• Readable - The file must be readable by the current user.
• Writable - The file and its containing folder must be writable by the current user.
• Ownership - The file must be owned by the current user and it must belong to a group that has the current user as a member.
• Unlocked - The file must not be locked or otherwise marked as immutable.
• Not Busy - The file must not be marked as “busy.”

A: To see or update Hyperspace’s settings, select “Settings” from the “Hyperspace” menu in the menu bar.

The settings are:

• Minimum File Size - Files below the specified size will not be considered for reclamation. Increasing this size will speed up the preliminary scan for identical files by allowing Hyperspace to immediately skip more files without examining their content. Conversely, decreasing this size can potentially allow Hyperspace to find more files with identical content. A minimum size of zero means Hyperspace will examine files of any size.

• Allowed File Types - The list of file types that will be considered for reclamation. These file types are stored using Apple’s Uniform Type Identifier ("UTI") format, which provides a hierarchy for file types. For example, there is a UTI for JPEG and a UTI for PNG, but there is also a UT for “all images.” Using UTIs for the list of allowed file types can make the list a lot shorter, since more general UTIs can encompass many more specific UTIs.

  The default list of allowed file types is very conservative, which means that Hyperspace will not even consider many kinds of files for reclamation. To view the list of allowed types, click the “File Types…” button in the Settings window. To add to the list, click the “+” button in the lower-left corner of the file types window. The menu that appears contains a few additional preset file types, plus a “Choose Example File…” option:

• Select “Choose Example File…” to show a dialog box where you can select one or more files of the types that you want to allow. Additional allowed types will be added based on the files selected. If a selected file does not expand the allowed types, you will be asked whether to add it. For example, if the list of allowed file types already includes “all images” and you select a JPEG image file, you will be asked if you want to add that type to the list even though it does not expand the scope of the allowed types.

  If you click the “Allow Any File” button or select a file that has no known type (e.g., a file with no file name extension and no other type information), then Hyperspace will consider all files as candidates for reclamation. This will supersede all other allowed file types. Though the other allowed types will remain present in the list, they will be dimmed and disabled because they are overriden by the “any file type” item.

• To remove an allowed type, select it in the list and then click the “-” (minus) button in the lower left. Removing the “any file type” item will re-enable the other items in the list.

• Reclaim storage immediately - When enabled, file data that has been replaced with a space-saving clone will be removed immediately. When disabled, redundant data will be moved to the Trash instead. The Trash will have to be emptied (using the Finder or the Dock) before that space can be reclaimed.

  Moving redundant data to the Trash instead of deleting provides some insurance, in case something goes wrong during reclamation. Until you empty the Trash, you can always retrieve the non-clone version of a file that was replaced by a clone.

  On the other hand, reclaiming storage immediately is less likely to leave a temporary file “stranded,” requiring manual clean-up.

  If you’re confused about why there would be any “redundant data” at all, since Hyperspace reclaims space “without removing files,” you can learn more about how this works in another section of this document.

As mentioned earlier, the green and red “+” and “-” buttons can be used to add and remove folders to scan. Multiple folders provide more files to scan, of couse, but they also potentially allow more duplicates to be found.

Consider two folders, Documents and Downloads. A file in the Documents folder may have no duplicates anywhere within the Documents folder. Similarly, a file in the Downloads folder may have no duplicates anywhere within the Downloads folder.

But now consider selecting both the Documents and Downloads folders for a single scan. A file in the Documents folder may have duplicates in the Downloads folder, and vice versa. When these two folders are scanned individually, such duplicates would not be found. When scanned together, there are more possible pairs and more potential for duplicates.

The other reason to select multiple folders for scanning is that entire folders can be marked as “Source Only”, meaning that the files within those folders will never be modified. They will only be used as the “source” of a clone operation. This is useful if you want to ensure that nothing in a folder is modified during reclamation.

To designate a folder as “Source Only”, Control-click or right-click the folder’s icon in the main window when there are two or more folder selected, then choose the “Source Only” item from the context menu. A lock badge will appear over the folder.

Note that there must always be at least one available folder that is not marked as being source-only, otherwise no reclamation will be possible. Also note that a different source can be chosen manually for each group of identical files, and this includes the ability to manually override the source-only nature of individual files within a source-only folder.

A: When reviewing files, the following shortcuts may be useful:

• After selecting a file group in the list, the up and down arrow keys will move the selection.

• When a file group is selected in the list, press the space bar to preview its contents.

• The checkbox in the first column header will toggle the checkboxes for all the file groups in the list.

  If you want to check not just the checkboxes for every file group but also the checkboxes for every file within each group (as seen in the detail area at the bottom of the window when a group is selected), hold down the Option key when clicking the checkbox.

• Option-click the checkbox for the file group in the detail area at the bottom of the window to check all the checkboxes for every file within the group.

A: Files are made up of data, which is the actual content of the file, and metadata, which is data about the file’s data. Metadata includes things like the file’s name, creation date, modification date, ownership, permissions, and so on.

The standard macOS file system, APFS, has the ability to create multiple files that each have their own metadata but that share a single copy of the data. Since data is usually much larger than metadata for any file of a nontrivial size, this saves disk space.

The Finder’s “Duplicate” command uses this feature when it duplicates a file. For example, consider a 100 GB video file as the only file on a 256 GB disk, leaving 156 GB of free space. If you duplicate that file, you might think that would leave only 56 GB of free space (256 GB - 100 GB - 100 GB = 56 GB). And with only 56 GB of free space, duplicating that file again seems impossible.

But if you actually try this on an APFS volume in macOS, you’ll find that you can make a nearly unlimited number of copies of that 100 GB video file using the Finder’s “Duplicate” command without filling the disk. Furthermore, each copy will be nearly instantaneous. That’s because macOS is only creating and storing the relatively tiny amount of metadata needed for each newly created duplicate file. Only a single copy of the 100 GB of data exists, and it is shared by all the duplicates.

Hyperspace searches for files that have identical data, and turns them into space-saving clones of each other using this feature of APFS, leaving only one copy of the data that is shared by all the clones. The metadata for the files is preserved during this process. From your perspective, nothing appears to have changed. The files all look the same as they did before Hyperspace did its work. But under the covers, all the files now share a single copy of the data.

Importantly, all the files remain independent. Changes to one file do not affect any of the other files. As the files are changed, their data storage, which was previously completely shared, will start to diverge, one piece at a time. The files will still share the pieces they have in common, even as their data changes and is no longer exactly the same for all the files.

A: No. Symbolic links ("symlinks") and hard links are ways to make two entries in the file system that share the same data. This might sound like the same thing as the APFS clones used by Hyperspace, but there’s one important difference. With symlinks and hard links, a change to one of the files affects all the files. The files are not independent.

A: The first and most obvious limitation of APFS space-saving clones is that they only work on APFS volumes. While APFS is the standard file system for macOS, macOS can also read and write disks of other formats. Hyperspace can only reclaim space on APFS volumes.

Furthermore, APFS only supports space-saving clones for files that are all on the same volume. A “volume” is the thing you see as a “hard drive” icon in the Finder. Even though it’s common for a storage device to contain a single volume and appear as a single icon in the Finder, each physical storage device can actually have multiple volumes on it, so the distinction between storage devices and volumes is important. Clones only work within the same volume. They cannot cross volume boundaries.

Hyperspace’s tag line (“Reclaim disk space—without removing any files!”) is best explained by example. Let’s say you start with five identical 100 MB files, which occupy a total of 500 MB of disk space (5 x 100 GB). After running Hyperspace on those files and reclaiming disk space from them, you will be left with…five 100 MB files. The files will look exactly the same as they did before Hyperspace ran. You started with five files and you ended with five files. None of the files have been removed. That's what the tag line means.

Of course, after Hyperspace has done its work, those five files now occupy a total of only 100 MB of disk space, for a savings of 400 MB of disk space. You can read more about how this works elsewhere in this document.

But what did Hyperspace do to make this happen? There’s no getting around that fact that 400 MB of data was deleted somehow, right?

Here’s what Hyperspace does when it’s reclaiming space. First, one file in each group of identical files is designated as the “source” file. This file will not be modified in any way. (You can change which file is the source during review, or more broadly when adding a folder to scan.) Then, for each “target” file in the group, Hyperspace makes a space-saving clone of the source file, copies all the metadata from the target file into that clone file, and finally, when that clone file looks exactly like the target file in every possible way, the target file is replaced by the clone file.

That final “replacement” process can happen in two possible ways, depending on a setting in Hyperspace. One way is that the target file can be moved to the Trash as the clone file replaces it. The other way is that the clone file can be (atomically) moved on top of the target file, causing the target file to cease to be as it is entirely replaced by the clone file. Some of the trade-offs between two approaches are described with the documentation for the relevant setting.

Either way, as you can see, Hyperspace does indeed delete data. That’s the only way to get more free disk space, after all. But it does it in such a way that, when it’s done, everything should appear the same as it did before it started. You should have the same number of files with the same names in the same places with the same creation and modification dates, the same Finder labels, the same permissions, and so on.

And, yes, the files all remain independent of each other when it comes to any and all modifications. Changes to one file do not affect any of the other files. Everything really does look and work just like it did before Hyperspace reclaimed that 400 MB of disk space.

Hyperspace will attempt to scan almost any folder or volume, but it may encounter errors during the scanning process. These errors are all instances where Hyperspace tried to perform a task as part of the scan but was unable to complete it successfully.

Since scanning is a read-only process, the worst thing that can happen is that one or more files are not able to be scanned. Nevertheless, Hyperspace reports all these errors to let the user know why certain files that they thought might be eligible for reclamation were not included in the scan.

The possible scan errors are:

• File is Unreadable - If a file cannot be read, Hyperspace cannot determine if it is a duplicate.

• File is Owned by Another User - Only files owned by the current user and that belong to a group that has the current user as a member will be eligible for reclamation.

• File Information Unavailable - If an attempt to get information about a file fails for any reason, it will be skipped.

• File Not Found - A file might not be found because it has been moved, renamed, or deleted between the time Hyperspace got the list of directory contents and the time Hyperspace tried to read the file.

• File Is Immutable or Locked - If a file is marked as immutable or is “Locked” in the Finder, Hyperspace does not consider it eligible for reclamation and it will be skipped during the scan. You may be able to manually unlock the file in the Finder by selecting the file and then selecting “Get Info” from the “File” menu. Then uncheck the “Locked” checkbox in the Get Info window.

  There are other ways that a file might be marked as immutable as well, but if you don’t understand why a file is designated as immutable, it may be best not to change it.

• File Is Busy - If a file is marked as “busy,” it will be skipped. You can manually clear the “busy” bit on a file by running the command SetFile -a z myfile.txt from the Terminal.

  Note that a file being marked as “busy” in this way doesn’t necessarily mean that the file is actually in use by another app. The “busy” bit is just another piece of file metadata, like the file name or creation date, that is persistently stored by the file system. It could have been set years ago and never changed. Or it could have been set moments ago by an app that is using the file. There’s no good way to tell.

Most of these errors are caused by situations beyond the control of Hyperspace. Some could be overriden by Hyperspace (e.g., Hyperspace itself could try to clear the “busy” bit), but that would only increase risks. If you, the user, want to unlock files or clear busy bits, feel free. But Hyperspace will not presume to know that it should ignore such signals.

The same goes for permissions issues. A file owned by the current user may still have its permissions set such that it is not readable by anyone. Since it is owned by the current user, Hyperspace could change the permissions on the file to make it readable, but it will not do so.

In general, Hyperspace will not alter the attributes of files when those changes would override their current state. Again, if you, the user, want to modify the permissions, ownership, or other attributes of files to allow Hyperspace to read from and write to them, you are free to do so.

Hyperspace may encounter errors during the reclamation process. These errors are all instances where Hyperspace tried to perform a task during reclamation but was unable to complete it successfully. Hyperspace reports all these errors to let the user know why certain files that they thought would be reclaimed were not.

Reclamation is when Hyperspace actually modifies your data. To protect your data, certain kinds of errors will immediately stop the reclamation process. These are errors that cause the contents of the disk to be left in an inconsistent state, usually by “stranding” a file that Hyperspace was unable to clean up. As soon a single file is stranded, the reclamation process stops.

The “Reclamation Errors” window will show these kinds of errors in orange or red text, and each error of this kind will include clean-up instructions and a clickable link to reveal the stranded file in the Finder. You should manually clean up these files by either renaming them back to their original names or by deleting them, depending on what kind of operation failed, according to the error message.

Here are some of the possible reclamation errors:

• Clean-Up Failure - Depending on the Settings, Hyperspace may create, move, and rename various files during reclamation. If anything goes wrong, the goal is to restore all files to their state before the reclamation was attempted. If something goes wrong during this clean-up process, one or more files may be left ”stranded” on the disk.

  These are files that Hyperspace tried to clean up, but it was unable to do so due to an error. It is up to the user to remedy the situation. The most serious example is when a file was renamed aside before being replaced by a space-saving clone, and the cloning process failed, and the file could not be renamed back to its original name. In this situation, the user must manually rename the file back to its original name. The “Reclamation Errors” window will include instructions and a link that will reveal the stranded file in the Finder.

  Less serious stranding errors occur when a temporary file created by Hyperspace could not be cleaned up. These files can safely be deleted.

  IMPORTANT: Please read the error message carefully to ensure that you can distinguish between a temporary file that can safely be deleted and one of your files that was renamed aside and needs to be renamed back! Do not accidentally manually delete your own files!

• File is Unreadable - If a file cannot be read, Hyperspace cannot use it as the source for a space-saving clone.

• File is Owned by Another User - Only files owned by the current user and that belong to a group that has the current user as a member can be reclaimed.

• File Information Unavailable - If an attempt to get information about a file fails for any reason, it cannot be reclaimed.

• File Not Found - A file might not be found because it might have been moved, renamed, or deleted between the time it was scanned and the time an attempt was made to reclaim it.

• File is Immutable or Locked - If a file is marked as immutable or is “Locked” in the Finder, Hyperspace does not consider it eligible for reclamation and it will be skipped. You may be able to manually unlock the file in the Finder by selecting the file, selecting “Get Info” from the “File” menu, and then unchecking the “Locked” checkbox in the Get Info window.

  There are other ways that a file might be marked as immutable as well, but if you don’t understand why a file is designated as immutable, it may be best not to change it.

• File is Busy - If a file is marked as “busy,” it will be skipped. You can manually clear the “busy” bit on a file by running the command SetFile -a z myfile.txt from the Terminal.

  Note that a file being marked as “busy” in this way doesn’t necessarily mean that the file is actually in use by another app. The “busy” bit is just another piece of file metadata, like the file name or creation date, that is persistently stored by the file system. It could have been set years ago and never changed. Or it could have been set moments ago by an app that is using the file. There’s no good way to tell.

Most of these errors are caused by situations beyond the control of Hyperspace. Some could be overriden by Hyperspace (e.g., Hyperspace itself could try to clear the “busy” bit), but that would only increase risks. If you, the user, want to unlock files or clear busy bits, feel free. But Hyperspace will not presume to know that it should ignore such signals.

A: Yes. An explanation of possible reclamation errors appears elsewhere in this document. But those are just the errors that Hyperspace can detect. There are many kinds of errors that it cannot detect.

Depending on the Settings, Hyperspace may replace many different kinds of files with space-saving clones. This includes files created by other applications or macOS itself that might be in active use. There is no way for Hyperspace to cooperate with all other applications and macOS itself to coordinate a “safe” time for those files to be replaced, nor is there a way for Hyperspace for forcibly take exclusive control of those files.

This leads to scenarios where other applications or parts of the system might experience unexpected results. For example, if an application is in the middle of writing to a file, and that file is replaced with a space-saving clone by Hyperspace, it is possible that the application will be blissfully unaware and will complete its write operation on the old version of the file, not realizing that file has been replaced by a clone of what the file looked like moments ago. An application might also encounter an error when trying to write to a file that Hyperspace has just replaced.

There are many, many possible situations like this that may occur if Hyperspace and some other process are trying to modify the same file at the same moment in time. Hyperspace includes many measures to prevent problems like this from happening, but nothing can prevent it entirely.

For best results, run Hyperspace when no other applications are running.

A: Hyperspace includes many features to decrease the likelihood that something will go wrong during reclamation.

• Allowed File Types - Only files with types in the list of allowed types are considered for reclamation. All other file types are ignored.

• Ignored Directories - Certain directories are entirely ignored by Hyperspace. This includes the /System directory (which is read-only anyway), the Library directories in your home directory and at the top level of the disk, and any kind of “bundle” directory. This includes all applications (i.e., .app bundles) as well as things like Apple Photos libraries (i.e., .photoslibrary bundles).

• Ignored Files - Files known to belong to the system, like .DS_Store files, are ignored. Any file that is unreadable by the current user or that has ownership information that cannot be reproduced by the current user is ignored. Any file that that is backed by a cloud storage service (e.g., iCloud Drive, OneDrive, and recent versions of Dropbox) in a way that the app can detect is ignored.

• Just-In-Time Validation - Since the processes of scanning and reclamation may be separated by some time, the reclamation process will do one final validation before replacing a file with a space-saving clone. If anything has changed since the scan (e.g., if the contents of one of the files has changed so it is no longer identical) then it will not be touched.

• Moving Redundant Data to the Trash - When replacing a file with a space-saving clone, the redundant data may optionally be put into the Trash, rather than being deleted immediately. This allows the old version of the data to be recovered at any time until the Trash is emptied.

Some of these safety features can be modified in Settings, but not all of them. Future versions of Hyperspace may allow more safety features to be disabled.

A: Increasing the amount of free disk space on APFS volume can only happen when nothing references some chunk of data. Only then can the space taken by that data be added back to the pool of free space.

If Hyperspace is configured to put redundant data in the Trash, the space taken by that data cannot be freed until the Trash is emptied.

APFS also supports snapshots, which preserve the contents of a volume at a given moment in time. The Time Machine backup feature of macOS creates local snapshots as part of its backup process. Even if a file is deleted, the space taken by that file cannot be freed if it is still part of one or more snapshots.

The local snapshots created by Time Machine are automatically removed when they are no longer needed, so the space taken by deleted files will eventually be freed. But it may be a day or more before this happens. (There are ways to force local snapshots to be deleted, but that is beyond the scope of this document. I recommend just waiting.)

A: When Hyperspace replaces a file with a space-saving clone, it attempts to preserve all metadata associated with that file. This includes the creation date, modification date, permissions, ownership, Finder labels, Finder comments, whether or not the file name extension is visible, and even resource forks. If the attempt to preserve any of these piece of metadata fails, then the file is not replaced.

If you find some piece of file metadata that is not preserved, please let us know.

A: Hyperspace considers the contents of a file’s resource fork to be part of the file’s data. Two files are considered identical only if their data and resource forks are identical to each other.

While a file is replaced by a space-saving clone during reclamation, its resource fork is preserved.

A: There is no easy way to check if two files are already clones of each other. Hyperspace itself makes a “best effort” to determine if two files with identical content are already clones of each other, and it skips them if it thinks they are.

A: Maybe, if the failure you’re trying to protect against is one where some part of your storage device or file system gets corrupted while another part remains functional. There’s no denying that having more copies of data is better than having fewer. That said, actual backups (i.e., copies of the data that are kept elsewhere, on a different storage device) offer much better protection against data loss.

A: Yes. Consider a 256 GB disk containing five space-saving clones of the same 100 GB video file. Thanks to the magic of cloning, those five files only take up a total of 100 GB on the disk. But if you tried to naively copy the contents of that disk to another 256 GB disk, the total amount of data to be copied would be 500 GB (5 x 100 GB), which would would not fit on a 256 GB drive. A sufficiently clever file copy operation could reproduce the clones on the target drive, but most file-copying software—including the Finder—does not do that.

Also keep in mind that most backup software does not attempt to reproduce cloned files. You may need a larger disk than you think in order to hold a complete copy of your data.

A: Yes.

A: If you have any more questions, contact us.