Backing Up Your Mac: The Online Appendixes Info about nearly 100 Mac backup products and services!

Welcome! If you want to compare features in Mac backup products and services, you’re in the right place. The content here is free to all, but it is associated with a commercial book, written by Joe Kissell and published by alt concepts inc. The book helps you figure out your best strategy for making backups in OS X, and then it covers all the details of set up, testing, maintenance, and restoration.

There are nearly 100 apps and services you can use to back up a Mac, and the list is constantly changing. In Backing Up Your Mac: A Joe On Tech Guide, I go into great detail about developing a backup strategy, selecting media, setting up a backup system, and recovering data when the need arises. I also discuss the criteria you should consider when choosing backup software. But rather than list them all in the book, I’ve moved most of the details to this online appendix for easier updating. This appendix covers only consumer apps (not enterprise-oriented software or command-line tools).

Although I’ve tried to be thorough and accurate, I haven’t listed every single feature, nor do I rate or rank backup apps. However, I do make specific recommendations in Backing Up Your Mac: A Joe On Tech Guide. I will update this page from time to time as features and prices change, and as errors are discovered.

On this tab:

On other tabs:

All the backup programs on this tab can store data on local media (such as an external hard drive). Those in the top table offer either or both of the two crucial backup varieties—a bootable duplicate (an exact copy of your entire startup disk that you can use to start your Mac if your main disk fails) or versioned backups (copies of your files as they appeared at many points in time). The bottom table includes apps that can sync or copy files to another location, but without either of those major backup features. (Some of these products also appear on the Online Services tab.)

Last updated: December 4, 2016

Software for Versioned Backups or Bootable Duplicates

Product Name Version Price Bootable
Duplicates
Versioning OS X
Compatibility
Available for
Other Platforms
Hard Disk Disk Image CD/DVD Media
Spanning
Network
Servers
Automount Online Storage Client-Server Peer-to-Peer Syncing Pruning Rolling
Backups
Snapshots File List Selectors Exclusions Delta
Encoding
Deduplication Compression Encryption Restore
Feature
Scheduling Can Wake Up/
Turn On Mac
Change
Detection
Metadata
Support
Notes
Acronis True Image
2017 for Mac
Prices start at $34.99 for one computer, including 50 GB of cloud storage; additional cloud storage available for an extra fee. See note. Yes (see note) 10.8–10.12 Windows Yes Yes Yes Yes Yes Yes Yes Min. once/day Not tested Creates images that can be restored to a bootable state, as well as a recovery drive, but not bootable duplicates as such. Can store full images in the cloud, bandwidth and data caps permitting. Stores last 10 system states.
Arq 5.5.2 $49.99; cloud storage extra No Yes 10.7–10.12 Windows Yes [b] Yes Amazon Cloud Drive, S3 (and S3-compatible targets), and Glacier; Dropbox; DreamObjects; Google Drive and Google Cloud Storage; OneDrive; SFTP; local, network, and NAS folders No Yes Yes Yes Yes Yes Yes Yes Yes Min. once/hour A+
Backuplist+ 8.5.5 Donation suggested Yes Yes 10.8–10.12 Yes Yes [c] Yes Yes Yes Limited Limited Yes Min. once/day A+
Carbon Copy Cloner 4.1.10 $39.99 Yes [a] Yes 10.6–10.12 Yes Yes [c] Yes See note. Yes Yes [g] Min. once/hour Yes A+ Can back up to a remote volume, if authentication package has been installed on that computer.
ChronoSync 4.7.1 $49.99 Yes [a] Yes 10.8–10.12 Yes [b] [c] Yes Yes Amazon S3, Google Cloud Storage, SFTP Yes Limited Yes Yes Limited Min. once/min wake only SmartScan algorithm A Some features require ChronoAgent, an additional $14.99 purchase.
ChronoSync Express 1.1.3 $29.99 No Yes 10.8–10.11 Yes [b] [c] Yes Yes Yes Limited Yes Yes Limited Min. once/min No A A somewhat limited version of ChronoSync that operates only on items in your home folder.
Clone X 4.3.2 $29.99 Yes No 10.6–10.12 Yes [b] [c] Yes Yes None C Can also create bootable DVDs and copy minimal systems, or systems without Users folder.
CloudBacko 1.9.2 Home version: free; Lite version: $9; Pro version: $39; cloud storage extra No Yes 10.6–10.10 Windows Yes [b] Yes Amazon S3, Dropbox, FTP/SFTP, Google Cloud Storage, Google Drive, Microsoft Azure, OneDrive, OpenStack, Rackspace Cloud Files, others No No No See note. Yes Yes No No Yes Yes Yes Yes Min. once/day. See note. Not tested. Can spread backup data across multiple cloud destinations. Home and Lite versions have limited control over pruning; Pro version offers complete control. Home version has no scheduling (manual backups only). Uses (and includes) Java, and has a pretty ugly, un-Mac-like user interface.
CopyCatX 5.1 $59.95 Yes No 10.6–10.10 Yes Yes [c] Yes Yes No (See note.) None Unable to test Demo version doesn’t support duplicates.
CrashPlan 4.8.0 Free; subscriptions to online storage start at $5 per month for unlimited data No Yes 10.5–10.12 Windows, Linux, iOS Yes Yes Proprietary (See note.) Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Min. once/day for free version. With a subscription, automatic; min. once/minute. Dynamic A Can back up to a local hard drive, to another computer running CrashPlan, or to the company’s online storage. Uses (and includes) Java.
Data Backup Pro 4.0 $49.99 Yes Yes 10.5–10.11 Yes [b] Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Min. once/min Yes C
Déjà Vu 4.8.8 $29.00 Yes Yes 10.5–10.12 Yes [b] [c] See note. Yes Yes Yes No (See note.) Limited Min. once/day C File list stored in a separate text file on disk. Toast includes a version of Déjà Vu that supports media spanning.
DollyDrive 3.24 Prices (for online storage) range from $10/month for 250 GB to $55/month for 2 TB. Yes Yes 10.5–10.12 iOS Yes Proprietary Yes Yes Yes Yes Yes Yes Syncing (Dolly Space) is continuous; for backups, min. once/hour Dynamic Not tested
Duplicati 2.0.1.30 Free (donations requested; online storage extra) No Yes 10.5–10.12 Windows, Linux Yes Yes Amazon Cloud Drive, Box, FTP, Google Drive, OneDrive, Rackspace, S3, SFTP, SSH, WebDAV, others Yes Yes Yes Yes Yes Yes Yes Min. once/second Not tested
FoldersSynchronizer X 4.1.1 $40.00 Yes No 10.9–10.11 Yes [b] [c] Yes Yes Yes Min. once/min C
ForeverSave 2.1.5 $14.95 No See note. 10.6–10.11 Yes [b] [c] Yes Yes Yes Yes Automatic when switching apps, or min. once/second Not tested Stores versioned backups only of files created by document-based apps. Also adds autosave feature to almost any app.
Get Backup Pro 3.3 $19.99 See note. Yes 10.5–10.12 Yes [b] Yes Yes Yes Yes Limited Limited Yes Yes Yes Yes Min. once/15 minutes This version not tested; version 2.3.2: B The version of Get Backup Pro sold in the Mac App Store does not create bootable duplicates.
GoodSync Desktop
for Mac
10.0.0 $29.95 No Yes 10.7–10.12 Windows Yes [b] Yes Amazon Cloud Drive, FTP, Google Drive, SFTP, OneDrive, S3, WebDAV, others Yes Yes Yes Yes Yes Yes Automatic on file change or min. once/minute Not tested
Instant Backup 1.8.2 $9.95 No Yes 10.5–10.11 Yes Yes [c] Yes FTP Yes Yes Yes A+ All backups go onto a disk image.
Intego Backup
Manager Pro
1.1 $39.95; bundled free with some LaCie drives Yes Yes 10.5–10.11 Yes Yes Yes Yes Yes Yes FTP, SFTP Yes Yes [e] Yes Yes Yes [g] [g] Yes Min. once/minute Yes C This is a customized version of Intego’s Personal Backup. Hasn’t been updated since 2011.
JumpVault Pro 2012.1.0 $79.99 No Yes 10.4–10.8 Windows Yes No No No Yes No No No Yes Yes Min. once/day Yes Scanning Not tested Uses a Java app. Hasn’t been updated since 2012.
Mac Backup Guru 6.2.2 $29.00 Yes Yes 10.9–10.12 Yes No No Yes Yes No No No No No No No No Min. once/day No Scanning Not tested
Memeo Premium
Backup for Mac
2.5.141 $49.95 No Yes 10.4–? Windows Yes [c] Yes Yes See note. See note. Presets Yes Yes Yes Automatic on file change Dynamic C Although Memeo Backup lists all versions of your backed-up files, it doesn’t do so by snapshot; you have to pick the desired version for each and every file you want to restore. Hasn't been updated since 2009.
NTI Shadow 5.0.0.52 $39.99 Yes Yes 10.5–10.9 Windows Yes [b] [c] Yes Yes (See note.) Yes Yes Automatic on file change, or min. once/min Dynamic This version not tested; version 4.x: C Uses the term “versioned” to refer to rolling versioned backups.
Personal Backup
(part of Mac Premium
Bundle X9)
10.9 $69.99; 3-user Family Pack, $139.99 Yes Yes 10.8–10.12 Yes Yes Yes Yes Yes Yes FTP, SFTP Yes Yes Yes [e] Yes Yes Yes [g] [g] Yes Min. once/min Yes B
QRecall 2.0.7 $40.00 Yes Yes 10.8–10.12 Yes [b] Yes Yes Yes Yes Limited Yes Yes Yes Yes Yes Automatic on file change or min. once/min Yes Dynamic A
QuickBack
(part of SpeedTools
Utilities Pro)
3.9 $29.95 Yes No 10.5–10.9 Yes Yes Yes Yes [g] [g] Min. once/day Not tested
Retrospect Desktop 13.5.0.173 $119 Yes [a] Yes 10.6–10.12 Windows Yes [b] Yes Yes Yes Amazon S3, Amazon Glacier, Dropbox, Google Cloud Storage, WebDAV, regional cloud storage providers Yes Yes Yes Yes Yes Yes Yes (see note) File level only Yes Yes Yes Min. once/hour; schedule-free operation requires use of Proactive Backup feature Yes Dynamic A Includes a Block-level incremental backup option, which, when enabled, copies only file deltas after the initial backup.
Rhinoback 5.5.7.0 Prices range from free (500 MB) to $49.95/month (20 GB); additional storage available. No Yes 10.5–10.8 Windows, Linux Yes Yes Proprietary Yes Yes Yes Yes Yes Yes Yes Yes Yes Min. once/day Dynamic Unable to test Uses AhsayOBM software.
SmartBackup 4.1 $29.99 Yes Yes 10.10–10.12 Yes [b] [c] Yes Yes Yes Limited Yes Yes Min. once/day B
Stellar Drive Clone 3.5 $39.00 Yes No 10.5–10.11 Yes Yes [c] Yes None Not tested Also creates a bootable restore DVD.
Syncovery
Standard Edition
7.65a $34.90 No Yes 10.4–10.12 Windows, Linux Yes [b] [c] Yes Yes Yes Yes Yes Yes Yes Min. once/sec Dynamic A Formerly called Super Flexible File Synchronizer.
Syncovery
Professional Edition
7.65a $59.90 No Yes 10.4–10.12 Windows, Linux Yes [b] [c] Yes FTP, Google Drive, HTTP, SFTP, S3, WebDAV Yes Yes Yes Yes Yes Yes Yes Yes Yes Automatic on file change or min. once/sec A Formerly called Super Flexible File Synchronizer.
SuperDuper! 2.9.1 $27.95; free “clone-only” version available Yes No 10.8–10.12 Yes Yes Yes [d] Yes [g] [g] Min. once/min Scans and copies in a single pass A+
Sync!Sync!Sync! 6.0.0 $16.00 No Yes 10.7–10.11 Yes [b] [c] Yes Yes Yes Yes Yes Min. once/day C
Synchronize Pro X 6.8.4 $49.95 Yes Yes 10.5–10.12 Yes [b] [c] Yes Yes Yes Yes Yes Automatic on file change, or min. once/min Yes Dynamic (optional) B
Synk Standard 7.0.12 $40.00 Yes Yes 10.6–10.10 Yes [b] [c] Yes Yes See note. Yes Yes Live, continuous sync, or min. once/hour Dynamic B Supports live synchronization between two Macs, optionally including versioned backups of changed/deleted files. Not quite the same as peer-to-peer backup, but it could serve a similar purpose.
Synk Pro 7.0.12 $60.00 Yes Yes 10.6–10.10 Yes [b] [c] Yes Yes See note. Yes Yes Yes Live, continuous sync, or min. once/hour Dynamic B Supports n-way synchronization. Also supports live synchronization between two Macs, optionally including versioned backups of changed/deleted files. Not quite the same as peer-to-peer backup, but it could serve a similar purpose.
Techtool Pro 8.0.4 $99.99 Yes No 10.4–10.11 Yes Yes [g] None Not tested
Time Machine 1.3 Included with macOS No Yes 10.5–10.11 Yes Yes Limited See note. Yes Yes [e] Limited 10.7 and later only Automatic; min. once/hour Dynamic B When used with a Time Capsule or another Mac, Time Machine can connect automatically to the network device without mounting it in the Finder—though it does mount a disk image automatically.
Tri-Backup 8.0.6 $69.99 Yes Yes 10.6–10.12 Yes Yes Yes See note. Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Min. once/min C Backups can span discs, but individual files can’t. Uses the term “Evolutive Mirror Backup” for versioned backups.
Tri-Backup Pro 8.0.6 $99.99 Yes Yes 10.6–10.12 Yes Yes Yes See note. Yes Yes FTP Yes Yes Yes Yes Yes Yes Yes Yes Yes Min. once/min C Backups can span discs, but individual files can’t. Uses the term “Evolutive Mirror Backup” for versioned backups.

Notes

[a] Can create bootable duplicates over a network.
[b] Only if created by user.
[c] Only if mounted in the Finder.
[d] Can back up to disk images on servers, but not directly to server volumes.
[e] Uses hard links; incremental updates function as their own snapshots.
[f] Copies only changed blocks, but modifies the entire file on the destination.
[g] Only for disk images.

Synchronization and Copying Products

The software in the following table supports neither bootable duplicates nor versioned backups, and therefore doesn’t qualify as true backup software, but it can in some cases provide limited, informal backups.

Product Name Version Price OS X
Compatibility
Available for
Other Platforms
Hard Disk Disk Image CD/DVD Media Spanning Network
Servers
Automount Online Storage Rolling
Backups
Selectors Exclusions Delta
Encoding
Compression Encryption Restore
Feature
Scheduling Can Wake Up/
Turn On Mac
Change
Detection
Metadata
Support
Notes
AASync 3.6.7.0 Free for local syncs only; $29 for local-to-remote 10.6–10.9 Windows Yes [b] [c] Yes FTP, SFTP Yes None Yes C
ArchiveMac 1.2.7 $24.99 10.5–10.6 Yes; see note. Yes Yes C Designed only for archiving files to optical discs. Supports archiving to Blu-ray discs as well.
FileSync 2.2 Free 10.5–? Yes [b] [c] Yes Yes Min. once/minute Unable to test
Folder Backup 5.0 €20 (about $26) 10.5–10.11 Yes Yes Yes Yes None A+ All backups go onto a disk image.
GrabBack 1.4.2 Free 10.5–? Yes [b] [c] Yes Yes Limited None C
iBackup 2014 7.6 Free 10.3–10.10 Yes [b] [c] Yes Yes WebDAV (See note.) Limited Presets Yes Yes Min. once/day A WebDAV volumes must already be mounted in the Finder.
JaBack 11.00 Free 10.5–10.11 Windows Yes [b] [c] No Yes No FTP Limited Limited No Yes No Yes Min. once/second No Not tested. Uses a Java app.
Match 1.3 $49.00 10.4–? Yes [b] [c] Yes Yes None C Hasn’t been updated since 2007.
Snap Backup 6.0 Free 10.5–10.11 Windows, Linux Yes [b] [c] Yes Yes Yes None Unable to test Uses a Java app.
StuffIt Archive
Manager (part of
StuffIt Deluxe)
16.0 $49.99 10.6–10.12 Windows Yes [b] Yes Yes Yes FTP, Dropbox, Google Drive, OneDrive Yes Yes Yes Min. once/day Unable to test Unable to copy some of the metadata test files.
Synchronize X Plus 4.3.3 $29.95 10.5–10.12 Yes [b] [c] Yes Yes Yes Yes None C

Notes

[b] Only if created by user.
[c] Only if mounted in the Finder.

Feature Explanations for This Tab

Bootable Duplicates: If the software can create an exact copy of your entire startup disk such that you can use the copy to boot your Mac, it gets a “Yes” in the Bootable Duplicates column. Note, however, that not all such programs are created equal. For example, those marked with footnote [a] can perform the unusual feat of making a bootable backup on a drive connected to another Mac on your network. Also see the Metadata Support column, as faithful copying of metadata is important for a good duplication program.

Versioning: A versioned backup starts with a complete copy of all the files in one or more folders. The next time the backup runs, your backup software performs an incremental update, which means it copies only those files that are new (or newly modified) since the last backup. If the software supports versioning, it means the backup program adds the new or changed data to the backup without overwriting the files already there. That way, you can retrieve many different versions of a given file, and if you delete it on your hard disk, you can still find it in your backup.

OS X Compatibility: This column lists the versions of OS X the program supports, as reported by the developer. A “?” in this column simply means the developer hasn’t specifically stated compatibility (beyond the version listed, if any).

Available for Other Platforms: A number of these Mac backup programs also come in versions for Windows and/or Linux. If you need to back up several computers running different operating systems, you may appreciate the convenience and familiarity of a single tool that works on all of them. Usually, though not always, if you create versioned backups with a multi-platform program, you can open and restore your files from another platform than the one you used to back them up. On the other hand, note that a few of the cross-platform programs have truly hideous user interfaces that were either written in Java without any consideration for the Mac aesthetic, or very badly ported from another operating system.

Hard Disk: Almost all backup programs can store backups on an internal or external hard disk. (Exceptions include those that use only optical media or DV camcorder tapes as destinations.)

Disk Image: Disk images are useful as containers that can organize, compress, and/or encrypt backups. Some backup programs (see the Notes column) always store backups in disk images, though that image may itself be located on various other media. Other programs optionally create disk images in lieu of storing “raw” files directly on the media. And many can store files on disk images only if you’ve manually created them using Disk Utility and mounted in the Finder (footnote [b]), though that strikes me as more hassle than I’d want to endure on a regular basis.

CD/DVD: Some backup programs can write directly to a SuperDrive or other optical drive. Others have “built-in” support for optical media in the sense that you can choose your optical drive as a destination directly within the program, but the software still relies on OS X’s disc burning mechanisms (and inherits its limitations). Both of the foregoing categories merit a “Yes” in this column. Many backup programs, though (marked with footnote [c]), can save files to an optical disc in a roundabout way: you put a disc in, mount it in the Finder, choose it as your backup destination, and then, after the backup has run, use the Finder to burn it.

Media Spanning: If your backup (or, in some cases, a single file) is too large to fit on a single CD or DVD, some backup programs can split it so that it spans more than one disc.

Network Servers: Most backup programs can save your files to any volume that’s mounted in the Finder—including other Macs using Personal File Sharing (AFP or SMB), PCs sharing disks with Samba (SMB), and WebDAV servers. However, beware: the fact that your backup program lets you store your files on one of these servers doesn’t guarantee that your data will be stored intact. In particular, some non-Mac network volumes are likely to munge Mac metadata unless the backup program takes special pains to enclose your data in a disk image or other archive file to preserve all those bits and pieces.

Automount: Most network servers require you to enter a user name and password to mount them. Some backup programs can store your login credentials for the backup server and automatically mount it for you when your backups run, saving you the hassle of doing this manually beforehand.

Online Storage: If you have an account on a network server that uses protocols such as FTP, SFTP, SSH, or WebDAV, you can to back up your files directly to them by using a program that supports the protocol you need. (Note that FTP is an inherently insecure protocol. Don’t use it for backups unless the files you’re sending across the network have already been encrypted, or your session is protected with a VPN connection.) Other services, such as Amazon.com’s S3 (Simple Storage Service), also provide inexpensive, secure file storage in the cloud. In addition, numerous online storage and backup services have proprietary systems that can be accessed only with their own software.

Client-Server: In this table, when I say “Client-Server,” I mean the following: You install a program (the backup server) on a computer on your local network, and then you install another program (the backup client—which in some cases is identical to the server software) on your other computers. The clients connect to the server without requiring that any volumes be mounted in the Finder on either end, and all files are backed up onto a drive attached to the server. Only a few of the programs listed here function in this type of client-server mode, though many of them can back up files over a network in other ways.

Peer-to-Peer: Meet Ann and Bob. Ann backs up her files over the network (local or remote) onto a drive attached to Bob’s computer, while Bob backs up his files over the network onto a drive attached to Ann’s computer. This sort of arrangement is called peer-to-peer (P2P) or mutual backups. Although many programs can be coaxed into producing this end result, a few are explicitly designed to do this easily, without requiring separate client and server software or complicated configurations on each computer.

Syncing: Some backup apps can also sync files among various devices, either directly over your local network or via the cloud. Many of the apps in the second table also sync files, but without performing other backup functions.

Pruning: Let’s say you put 10 files in your backup. Over time, because you change file #3 quite often, you accumulate a lot of copies of that file in your backup. If it’s a big file, that can result in your backup occupying a significant amount of space. Some backup programs can automatically delete only older files in your backup to make space for new ones. For example, you might be able to specify that your backup contains a maximum of 10 versions of any particular file, or that any additional copies more than 90 days old are deleted. Any scheme whereby a backup program automatically and selectively deletes older files from an backup gets a “Yes” in this column.

Rolling Backups: Some programs update backups additively but not incrementally. In other words, if you’re backing up your Documents folder, the program copies the entire folder every time it runs, regardless of how few files in it have changed. When backup programs do this, they sometimes give you the option of deleting the oldest complete backup after a certain number of runs (as opposed to deleting individual files) to make space on your backup media. I refer to this type of procedure as a rolling backup.

Snapshots: Snapshots apply only to programs that create versioned backups. By “snapshot,” I mean a picture of what your entire disk (or, at least, the entire set of files you’re backing up) looked like at the moment each backup session ran. With snapshots, you can easily see how many files appeared at a given time, and in one fell swoop, restore your disk to the way it appeared then. In most cases, programs that store snapshots give you a list or menu of all the times at which backups occurred, and when you select one of those, you can generally see all the versions of files in your backup as they appeared at that time—even those files that hadn’t changed recently and therefore weren’t copied on that particular run.

File List: For the purpose of these tables, when I refer to a “file list,” I simply want to know whether there’s some way I can see, from within the backup program, what files it has backed up (rather than having to dig around in the Finder). Not all file lists are created equal. Some are spiffy—color-coded, searchable, and intelligently hierarchical. Others are confusing and tedious to use. But I don’t distinguish niceness here, only whether or not there’s something in the app that could reasonably be construed as a file list.

Selectors: It goes without saying that virtually every backup program lets you select what folders or files you back up. But in this table, when I say “selectors,” I mean pattern-based rules for selecting files. For example: “Back up all the files with an extension of ‘.doc’ that are less than 500 MB in size.” Of the programs that offer selectors, some are much more sophisticated than others, but the point is that you have a way of specifying, usually with a few clicks, what kinds of files will be included in your backups. A close relative of the selector is the preset, which is basically a prebuilt selectors that chooses all files of a particular sort—for example, all the files that make up your Contacts database, or all your Mail files, or every MP3 file anywhere on your computer.

Exclusions: Once again, I’m not merely talking about the fact that you can manually deselect or exclude a particular file or folder. By “exclusion” here I mean a pattern-based rule for selecting files that will not be backed up. For example: “Omit all files over 2 GB” or “Omit files with a Red label in the Finder.”

Delta Encoding: Historically, most backup software has performed versioned backups on a file-by-file basis. In other words, if just 10 bytes of a 10 GB file change, that marks the file as modified, and the whole file must be copied on the next backup run. Some software, however, can copy only the individual bytes that have changed since the last backup, while other software copies slightly larger units called blocks. Copying just the delta—that is, the differences between the file at time A and the file at time B—is known as delta encoding, though you may see other terms, such as “sub-file,” “byte-level,” and “block-level” incremental updates. The advantage of such an approach is that backups go much faster after the initial run and take up far less storage space; this is particularly important when backing up over the Internet. The disadvantage is that restoring a file requires the backup software to reconstruct it by putting together the pieces from all its incremental backups. If even a single one of those incremental bits were to become damaged or lost, you might be unable to restore the file.

Deduplication: Simply put, deduplication is the process of ensuring that data stored on your backup destination volume isn’t duplicated—which reduces the amount of storage space required (sometimes dramatically), and can also speed up backups considerably. For example, if you have two copies of a file on your disk, a program that features deduplication will store only one copy on your backup media, along with a pointer to the other one (so that the file can be restored to either location with equal ease). In most cases, deduplication is done on a block-by-block or even byte-by-byte basis, so that when files are quite similar, only one complete copy of the file is stored, along with the differences found in the other version(s) so that any of them can be reconstructed. In other cases, it’s done at the file level—two identical files won’t be duplicated, but if the files are only 99 percent the same, they will be. Some implementations of deduplication can compare data from multiple computers, while others can deduplicate data only from a single source.

Compression: When a backup app compresses your files, they take up less room on your storage media—usually a good thing, as that reduces your costs and lets you store backups for longer periods of time before having to reuse your media. Compression is even more important when data is traveling over the Internet, because compressed data takes less time to send, and online storage costs are often much higher than the cost of local media. On the other hand, compressing files taxes your computer’s CPU, RAM, and disk, and having compressed files may add an extra complication when it comes time to restore data.

Encryption: As long as your backup media is under your physical control, encryption isn’t especially important. But if you store backup media offsite in any fashion, or if anyone else (a thief, say, or a nosy coworker) can get access to your backups, you might prefer that they not be able to see all your data. Some backup software can encrypt all the data on your backup media so that you won’t risk your private information falling into the wrong hands.

Restore Feature: A restore feature simply means that, with a button click or menu command, you can instruct your backup program to return files that you previously backed up to their original location (or, if you prefer, another location). Quite a few programs expect you to simply switch the “source” and “destination” and, essentially, redo your backup. A restore feature is most important with backup programs that store multiple versions of your files, because otherwise, sifting through a lot of different file versions by hand is going to be a real pain.

Scheduling: Traditionally, most backup programs have used a fixed schedule: you set a time (once a day, twice a week, or whatever—maybe in the middle of the night) and the software does its thing only at that time. For software that uses a fixed schedule, this column lists the most frequent option available (such as once per hour or once per day). Increasingly, though, backup programs offer some form of automatic operation (either by default or as an option), such as backing up files as soon as they change or running in the background every hour. In general, if a program can run once an hour or more frequently and it dynamically detects changed files (see just ahead) so that it needn’t do a full scan with each run, it is effectively schedule-free. On the other hand, some backup programs don’t support any kind of scheduling—they run only when you activate them manually.

Can Wake Up/Turn On Computer: For backup software that runs on a fixed schedule (once a day, say), it’s handy for it to be able to wake up your computer if it happens to be asleep then, or even turn it on if it’s off. These capabilities, though rare, save you from worrying that a schedule won’t run properly because your computer didn’t happen to be on or awake at the right time.

Change Detection: Some programs can detect file changes in real time, either by using OS X’s FSEvents (file system events) framework or by running in the background and employing proprietary methods to watch for changes. In whatever form, dynamic change detection reduces or eliminates the need for a time-consuming scan each time your backups run and, in some cases, enables continuous, real-time backups as your files change. (Even so, occasional full scans may be necessary.) Alternatively, some backup software scans and copies in a single pass, arguably a more efficient approach (depending on your needs) than scanning all your files and then making another full pass to copy them.

Metadata Support: Even though a file may appear to copy correctly, some important information about the file may be missing or incorrect—things like ownership, permissions, modification date, Finder flags, access control lists, and many others (collectively known as “metadata”). Theoretically, backup software should copy every piece of metadata perfectly, though in practice, many types of metadata are so insignificant or seldom used that no harm is done if they’re missing in your backups. Faithful copying of metadata is most crucial when making a bootable duplicate.

I used a tool called Backup Bouncer to test metadata support for as many of these programs as I could. Backup Bouncer checks a great many attributes, but it divides its results according to how significant the developer feels each one is: “critical,” “important,” and “other.” I’ve used the Backup Bouncer results to assign a “grade,” as follows:

  • A+: The software passes ALL of Backup Bouncer’s tests perfectly.
  • A: All “critical” and “important” attributes are copied correctly.
  • B: All “critical” attributes are copied correctly, but at least one “important” attribute is not copied correctly.
  • C: At least one “critical” attribute is not copied correctly.

Although metadata is in some cases very important, I urge you to take these test results (especially the “C” grade) with a grain of salt, for two reasons. First, because of the way Backup Bouncer groups its results, a fairly insignificant problem can sometimes result in a failed test in a “critical” category. And second, depending on the way a given backup program is designed and used, it may be irrelevant that certain attributes (such as file ownership) aren’t always copied correctly. Also, the difference between an “A+” and an “A” is effectively meaningless. So basically: don’t freak if your favorite program gets a less-than-perfect score—but do consider contacting its developer to suggest that they look into using Backup Bouncer to improve its metadata support in the future.

Where you see “Not tested” in this column, it means I haven’t taken the time to run the test—it’s time-consuming and not always worth the effort. “Unable to test” could mean any of several things: the software may not be compatible with the version of OS X on my test machine; it may be designed in such a way that it can’t work with Backup Bouncer’s test suite; or I may not have had access to a version of the program suitable for testing.

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