From efca1b4459533b3c1b8eb1b1b1a3d0a59d2c9b72 Mon Sep 17 00:00:00 2001 From: gilbertchen Date: Fri, 26 Feb 2016 00:59:04 -0500 Subject: [PATCH] Update README.md --- README.md | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/README.md b/README.md index 44bf1e2..4ed6739 100644 --- a/README.md +++ b/README.md @@ -171,17 +171,17 @@ to find the differences from previous backups and only then uploading the differ [Obnam](http://obnam.org) got the incremental backup model right in the sense that every incremental backup is actually a full snapshot. Although Obnam also splits files into chunks, it does not adopt either the rsync algorithm or the variable-size chunking algorithm. As a result, deletions or insertions of a few bytes will foil the [deduplication](http://obnam.org/faq/dedup). -Deletion of old backups is possible, but no cloud storages are supoprted. +Deletion of old backups is possible, but no cloud storages are supported. Multiple clients can back up to the same storage, but only sequential access is granted by the [locking on-disk data structures](http://obnam.org/locking/). It is unclear if the lack of cloud backends is due to difficulties in porting the locking data structures to cloud storage APIs. -[Attic](https://attic-backup.org) has been acclaimed by some as the [Holy Grail of bacups](https://www.stavros.io/posts/holy-grail-backups). It follows the same incremental backup model as Obnam, but embraces the variable-size chunk algorithm for better performance and better deduplication. Deletions of old backup is also supported. However, no cloud backends are implemented, as in Obnam. Although concurrent backups from multiple clients to the same storage is in theory possible by the use of locking, it is +[Attic](https://attic-backup.org) has been acclaimed by some as the [Holy Grail of backups](https://www.stavros.io/posts/holy-grail-backups). It follows the same incremental backup model as Obnam, but embraces the variable-size chunk algorithm for better performance and better deduplication. Deletions of old backup is also supported. However, no cloud backends are implemented, as in Obnam. Although concurrent backups from multiple clients to the same storage is in theory possible by the use of locking, it is [not recommended](http://librelist.com/browser//attic/2014/11/11/backing-up-multiple-servers-into-a-single-repository/#e96345aa5a3469a87786675d65da492b) by the developer due to chunk indices being kept in a local cache. Concurrent access is not only a convenience; it is a necessity for better deduplication. For instance, if multiple machines with the same OS installed can back up their entire drives to the same storage, only one copy of the system files needs to be stored, greatly reducing the storage space regardless of the number of machines. Attic still adopts the traditional approach of using a centralized indexing database to manage chunks, and relies heavily on caching to improve performance. The presence of exclusive locking makes it hard to be adapted for cloud storage APIs and reduces the level of deduplication. [restic](https://restic.github.io) is a more recent addition. It is worth mentioning here because, like Duplicacy, it is written in Go. It uses a format similar to the git packfile format, but not exactly the same. Multiple clients backing up to the same storage are still guarded by [locks](https://github.com/restic/restic/blob/master/doc/Design.md#locks). -A command to delete old backups is in the developer's [plan](https://github.com/restic/restic/issues/18). S3 storage is supported, although it is unclear how hard it is to support other clould storage APIs because of the need for locking. Overall, it still falls in the same category as Attic. Whether it will eventually reach the same level as Attic remains to be seen. +A command to delete old backups is in the developer's [plan](https://github.com/restic/restic/issues/18). S3 storage is supported, although it is unclear how hard it is to support other cloud storage APIs because of the need for locking. Overall, it still falls in the same category as Attic. Whether it will eventually reach the same level as Attic remains to be seen. The following table compares the feature lists of all these backup tools: