[DRBD-user] Snapshot with DRBD

Tomasz Chmielewski mangoo at wpkg.org
Thu Feb 14 13:14:12 CET 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


drbd at bobich.net schrieb:

(...)

>> 2.1. Snapshots
>>
>> Snapshots can be useful as part of an hourly backup system. Instead of 
>> shutting down all applications for the entire duration of the backup, 
>> you can shut them down for just the second or two needed to take a 
>> snapshot.
> 
> Which doesn't solve the original poster's problem of having to shut 
> things down for a consistent snapshot. :-(

There was a discussion on lkml about implementing filesystem freeze 
feature in ext3, juts like it is in XFS.
I think when LVM2 makes a snapshot of a XFS filesystem, it calls a 
xfs_freeze, so the filesystem and data should be consistent.

So, right now, using XFS would be a solution?


>> If your goal is to protect users from accidental deletion of files, 
>> you may want to take snapshots every hour, and leave the last few 
>> snapshots around; users who accidentally delete a file can just look 
>> in the snapshot.
> 
> There are much better ways of achieving this functionality. Snapshots 
> are not the way to do it. A stackable versioning file system like 
> Wayback (deprecated) and CopyFS achieve that in a much neater way.

They base on FUSE.

I don't think either of them can perform well when compared to 
traditional filesystems.


-- 
Tomasz Chmielewski
http://wpkg.org



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