On Mon, Aug 12, 2013 at 08:45:45AM +0200, Valerio Pachera wrote: > Hi, on my guest named 'backup' I have two vdi: 'backup' and 'backup_data'. > > backup 0 10 GB 3.8 GB 0.0 MB 2013-06-27 15:51 19093f 2 > backup_data 0 1.0 TB 408 MB 502 GB 2013-08-12 08:15 c8d149 2 > > The first one, as you can guess, contains only the OS. > > Write speed: > backup: 15 M/s > backup_data: 6 M/s > > The differences between the two are the size and that 'backup_data' > has several snapshots (21). > > What do you think about that? This is what copy-on-write takes from you when it saves you a lot of space by sharing objects between snapshots. When a write is executed, sheep will firstly copy the shared object and then write on it. So compared with pure write, COW write will spend one more read. Thanks Yuan |