[linux-lvm] Snapshots (overheads and 2.6 kernel status)

[Steve McIntyre]

On Mon, Nov 29, 2004 at 03:08:50PM -0000, C R Ritson wrote:
>Does anybody know how much overhead is involved in keeping a snapshot of
>an active volume (for 24 hours)? I am currently running LVM1 (waiting
>for snapshots in LVM2/device mapper) and am making a snapshot of my user
>volumes overnight. These are left available for 24 hours in the hope
>that users who damage a file will be able to get "yesterday's copy" from
>the snapshot without us needing to restore from tape. There is obviously
>some overhead involved, but does anyone know how much?

It can be quite significant, depending on your workload. I'm using
snapshots in a similar way, and I saw performance drop by a factor of
2 (or more) on our main NFS server. It's very useful to have the
snapshot, so we live with it.

-- 
Steve McIntyre, Plasmon                       smcintyre at software.plasmon.com
 
"C++ ate my sanity" -- Jon Rabone