On Jun 11, 2006, at 03:21, can you guess? wrote:
My dim recollection is that TOPS-10 implemented its popular (but again <100%) undelete mechanism using the same kind of 'space- available' approach suggested here. It did, however, support explicit 'delete - I really mean it' facilities to help keep unwanted detritus from shouldering out more desirable bits ('expunge' being the applicable incantation, which had an appropriate ring of finality to it). Tying into user quotas such that one user can't drive another user's most-recently-deleted content out of the system seems implicit in eschrock's comments.
There's also Plan 9's Venti [1]:
Venti is a network storage system that permanently stores data blocks. A 160-bit SHA-1 hash of the data (called score by Venti) acts as the address of the data. This enforces a write-once policy since no other data block can be found with the same address. The addresses of multiple writes of the same data are identical, so duplicate data is easily identified and the data block is stored only once. Data blocks cannot be removed, making it ideal for permanent or backup storage. Venti is typically used with Fossil to provide a file system with permanent snapshots.
Venti works in combination with Fossil [2]:
Fossil is the default file system in Plan 9 from Bell Labs. It serves the network protocol 9P and runs as a user space daemon, like most Plan 9 file servers. Fossil is different from most other file system due to its snapshot/archival feature. It can take snapshots of the entire file system on command or with an interval. These snapshots can be kept on the Fossil partition as long as disk space allows; if the partition fills up old snapshots will be removed to free up disk space. A snapshot can also be saved permanently to Venti. Fossil and Venti are typically installed together.
[1] http://en.wikipedia.org/wiki/Venti [2] http://en.wikipedia.org/wiki/Fossil_%28file_system%29 _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
