Retrospect is a family of software applications that back up computers running the macOS, Microsoft Windows, Linux, and classic Mac OS operating systems. It uses the client–server backup model, which means there must be a backup server application running on one computer and small-footprint client applications running on the other computers being backed up in either a single platform or mixed platform network. The destination may be a tape drive, a hard disk drive or cloud drive. The company's backup server application requires macOS or Windows, but versions of the client application can be run on Linux or Classic Mac OS.
The software was first developed by Dantz Development Corporation in the mid-1980s, initially for the Macintosh platform and later for Windows. With sales split evenly between the two variants and the Macintosh variant claiming 90% of its market, Dantz Development Corporation was acquired by EMC Corporation in 2004. Version 7.5, the first release of the Windows variant under EMC, added performance features needed by SMEs. In 2009, EMC indicated an intention to add an updated user interface and separate administration Console similar to that of the newly-released Macintosh variant version, but mandatory Windows security settings starting with Windows Vista/Server 2008 subsequently forbade UI interaction with an application auto-launched by a task.
Meanwhile the Macintosh variant "languished" at EMC, until "development was revived in 2008 when EMC hired back some of its former engineers"—including ex-Dantz ones. This resulted in the "premature"  release of a version of Retrospect Macintosh that was temporarily missing key operational features, even though it added the performance features of Retrospect Windows 7.5.
In May 2010, the software was sold to Roxio/Sonic Solutions. In 2011, following the purchase of Sonic Solutions by Rovi, development of the software was turned over to a privately held company. Since 2012 Retrospect Inc. has continued to sell two variants of backup server software that, while having nearly identical non-GUI code, operate differently[note 1]—with a view-only Dashboard substituting for a separate administration console in Retrospect Windows.
- Backup destinations
- Termed Media Sets[note 2]—allow media spanning and may contain one or more disks, in the Windows variant one or more superfloppies, one or more tapes or WORM tapes, one or more CD/DVD discs, or a single AFP/SMB file or Cloud storage account. If run using a non-Desktop Edition, the backup server is multithreaded so that multiple scripts can simultaneously back up to or restore from different Media Sets.
- Always versioned; do client-side file-level deduplication; can be  incremental, of subvolumes,[note 3] may exclude files;[note 4] optional optimizations include data compression, encryption of Media Sets and of data transfers between a particular client computer and the server. Moreover, volume-to-volume duplicates [note 5] of the latest versions of files in appropriate OS format can be made.
- Data sources beyond the usual filesystems
- Email accounts can be backed up and restored, or directly migrated and synced, for major services that support IMAP. Avid Media Composer devices are supported as sources for backup, copy/duplicate, archive, and restore scripts.
- Validation of backups and copies of backups
- Comparing byte-by-byte or via MD5 digest; using saved MD5, can be a separate verification script run outside the network's "backup window". Volume-to-volume duplicates in OS format of the latest versions of files can—unlike by OS—also be verified.
- Proactive scripts
- Are usually left running at times that are not in the network's "backup window", back up computers—frequently but not always mobile—transiently connecting to the network, determining backup priorities  by an "AI" algorithm that uses a decision tree supplemented by linear regression. They are an alternative to another application's window-cramming tape-only "multiplexed backup" capability.
- Success validation
- With e-mailing of notifications about operations to chosen recipients; for Backup runs these are now customized to include a one-line summary at the top, a subject line that includes the script name and number of errors and warnings, and an e-mail body that consists of the script log—pinpointing the errors and warnings. Monitoring with "Retrospect for iOS" is also available.
- Cloud Backup
- Cloud Media Set type enables backup/restore/utility operations on data stored with AWS-S3-compatible cloud storage providers including Dropbox, with Google Cloud Storage, and with Backblaze B2. WebDAV is also available.
Enterprise client-server features
Retrospect also supports several enterprise client-server backup features. These include:
- Disk-to-disk-to-tape capabilities that may incorporate file exclusion,[note 4] creating synthetic full backups; automated data grooming with GDPR exclusion rules, block-level incremental backup, and "instant" scanning of client volumes.
- Source file integrity
- Backing up interactive applications with pausing/unpausing of services via "script hooks".
- User interface
- Administration Console, user-initiated backups and restores, high-level/long-term reports supplementing the Administration Console, and integration with monitoring systems via "script hooks".
- Advanced network client support —which can be extended to "remote" clients anywhere on the Internet for Proactive scripts and user-initiated backups/restores, and cloud seeding and large-scale recovery.
Editions and Add-Ons
Retrospect is sold with varying backup server capability levels, called "Editions", at license–code prices  that cover one major version. The Edition is dictated by the number of "server OS" computers being backed up; it in turn specifies a maximum number of client computers. The Desktop Edition can be used where only desktop or mobile computers (or Linux servers ) are being backed up, non-multithreaded, to non-tape devices or to one non-autoloader tape drive. The Solo Edition "protects a single non-server computer and its external hard drives".
"Add-Ons", which activate additional backup server features via license codes, may also be purchased:
- backing up Microsoft Exchange servers or Microsoft SQL servers
- non-Desktop-Edition protection of NTFS open files, such as for continuously-running QuickBooks, on Windows systems
- backing up to multiple single tape drives simultaneously or to a multiple-drive tape library
- extending the bare-metal Emergency Recovery CD to adjust Windows boot volume drivers
- backing up and restoring more client computers than the maximum the chosen Edition specifies
- The terminology was changed in the 2009 Macintosh variant; this article will use whichever variant's term seems more precise, with the other variant's term as a footnote.
- Termed Backup Sets in the Windows variant; could be referred to as archive files, except that Retrospect uses the term Archive to refer to a backup operation that deletes data from a client's source drive once the data's backup is complete.
- To be used, a Subvolume must be defined to the Retrospect application, and is therefore currently termed a Favorite Folder in the Macintosh variant.
- Exclusion and/or inclusion is done with Selectors in the Windows variant; this misleading term has been changed to Rules in the Macintosh variant.
- The Duplicate operation is currently termed Copy in the Macintosh variant.
- Kissell, Joe (2007). Take Control of Mac OS X Backups (PDF) (Version 2.0 ed.). Ithaca, NY: TidBITS Electronic Publishing. pp. 24 (client–server), 127 (script), 165 (client–server), 128 (subvolume—later renamed Favorite Folder in Macintosh variant). ISBN 0 - 9759503 - 0 - 4. Retrieved 22 September 2017.
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Improved: Retrospect Dashboard has a new icon to differentiate it from the Retrospect application. Improved: Retrospect Dashboard launches when Retrospect is already running in Session 0 and includes explanatory message. Improved: Retrospect Dashboard's "Relaunch Retrospect" button displays an alert message when there is an execution running. Improved: Retrospect Dashboard includes improved media request text. Note: In a future update, Linux clients running on server-level Linux distributions will be treated as server clients.
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