Re: [zfs-discuss] simple question about snapshots

2012-07-12 Thread bofh
On Thu, Jul 12, 2012 at 7:32 PM, Bob Friesenhahn wrote: > On Thu, 12 Jul 2012, bofh wrote: >> When I do a snapshot, that file is part of the snapshot. But are >> changes within the file kept as well? > > Only the difference (at block level) between the snapshots is kept. If the > changed data was

Re: [zfs-discuss] simple question about snapshots

2012-07-12 Thread Bob Friesenhahn
On Thu, 12 Jul 2012, bofh wrote: When I do a snapshot, that file is part of the snapshot. But are changes within the file kept as well? Only the difference (at block level) between the snapshots is kept. If the changed data was changed 1000 times between the snapshots, then only the differe

[zfs-discuss] simple question about snapshots

2012-07-12 Thread bofh
When I do a snapshot, that file is part of the snapshot. But are changes within the file kept as well? In other words, is it useful to have snapshots of a postgresql database server? If a database file uses 10% of the pool, and changes 20% between each snapshot, would the pool run out of space a