Hello Eric, Thanks for your response. I have another question. This time regarding zfs send. I have updated the subject line to include "zfs send" question in this thread.
If the pool tank has 5000 descendent file systems and the snapshots are being taken using "zfs snapshot -r". Now I will be sending and receiving incremental snapshot to a second system using the following command. "zfs send -R -i <prev snapshot> <latest snapshot> | ssh <second_sysname> zfs recv -vFd tank" My question is: Is "zfs send -R " sends snapshot all at once OR does it send all the descendent snapshots serially(one after another) ? I am asking this because, if it sends serially, send/recv will take long time to finish based on the number of snapshots need to be send and this duration will gradually increase if number of snapshots also keep increasing. Is my assumption correct? Thanks, -- Rahul On Tue, Feb 1, 2011 at 5:05 PM, Eric D. Mudama <edmud...@bounceswoosh.org>wrote: > On Tue, Feb 1 at 10:54, Rahul Deb wrote: > >> Hello All, >> I have two questions related to "zfs snapshot -r" >> 1. When "zfs snapshot -r tank@today" command is issued, does it creates >> snapshots for all the�descendent file systems at the same moment? I mean >> to say if the command is issued at 10:20:35 PM, does the creation time of >> all the snapshots for descendent file systems are same? >> 2. Say, tank has around 5000 descendent file systems and "zfs snapshot -r >> tank@today" takes around 10 seconds to complete. If there is a new file >> systems created under tank within that 10 seconds period, does that >> snapshot process includes the new file system created within that 10 >> seconds? >> OR it will exclude that newly created filesystem? >> Thanks, >> -- Rahul >> > > I believe the contract is that the content of all recursive snapshots > are consistent with the instant in time at which the snapshot command > was executed. > > Quoting from the ZFS Administration Guide: > > Recursive ZFS snapshots are created quickly as one atomic > operation. The snapshots are created together (all at once) or not > created at all. The benefit of such an operation is that the snapshot > data is always taken at one consistent time, even across descendent > file systems. > > Therefore, in #2 above, the snapshot wouldn't include the new file in > the descendent file system, because it was created after the moment in > time when the snapshot was initiated. > > In #1 above, I would guess the snapshot time is the time of the > initial command across all filesystems in the tree, even if it takes > 10 seconds to actually complete the command. However, I have no such > system where I can prove this guess as correct or not. > > --eric > > -- > Eric D. Mudama > edmud...@mail.bounceswoosh.org > >
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