Sounded pretty simple, so I tried it. Like earlier attempts to "zfs send | zfs recv"... several minutes go by and NOTHING HAPPENS. The delay made me nervous (not knowing what was going on) so I aborted it from the NON-test system (sending to this remote system) and used tape to get it over there.
Now I am testing with about 20% of the actual message store so whatever the numbers are here, it will be safe to assume 5x longer on the other system. I start the move:
zfs send store@today | zfs recv newmail/store
It did NOTHING on the actual file system for 20 minutes. Meanwhile,
"zfs list" showed that it created the target filesystem and the target
filesystem usage was growing. When the target filesystem size matched the original filesystem, the data seemed to ALL SUDDENLY APPEAR ON THE DISK. I didn't trust it so I ran du and sure enough - 10's of thousands of user accounts were there. Pretty wild. Next test - 2nd snapshot. The 2nd snapshot should be ONLY the diffs and should be pretty quick. I guess the assumption is that there are no other snapshots. It has to be clean. Interesting.
This means I could use the daily snapshot - once done, move to the
new disk, take system down, take a 2nd snapshot, move the difs & ta-dah! Very cool stuff, this ZFS. Then I try part two.
bash-3.00# date && zfs send store@L8R | zfs recv newmail/store && dateHuh?! It sounds like I have to destroy the content on the new system to do this. This can't be right - or can it? It's a test system so I proceed.
Friday, June 11, 2010 10:55:49 AM CDT
cannot receive new filesystem stream: destination 'newmail/store' exists
must specify -F to overwrite it
bash-3.00# date && zfs send store@L8R | zfs recv -F newmail/store && dateOh yeah, I forgot, it duplicates the snapshot when you do this. No harm to get rid of that I suppose...
Friday, June 11, 2010 11:23:23 AM CDT
cannot receive new filesystem stream: destination has snapshots (eg. newmail/store@today) must destroy them to overwrite it
bash-3.00# zfs listThere! Now check to see that its all gone and note the filesystem sizes.
NAME USED AVAIL REFER MOUNTPOINT
newmail 41.4G 226G 44.0K /newmail
newmail/store 41.4G 226G 41.2G /newmail/store
newmail/store@today 187M - 41.2G -
store 41.4G 292G 41.2G /store
store@today 78.0K - 41.0G -
store@L8R 193M - 41.2G -
bash-3.00# zfs destroy newmail/store@today
bash-3.00# zfs listAfter a bit and while it's doing this, I switch over to another console and run zfs list:
NAME USED AVAIL REFER MOUNTPOINT
newmail 41.2G 226G 44.0K /newmail
newmail/store 41.2G 226G 41.2G /newmail/store
store 41.4G 292G 41.2G /store
store@today 78.0K - 41.0G -
store@L8R 193M - 41.2G -
bash-3.00# date && zfs send store@L8R | zfs recv -F newmail/store && date
Friday, June 11, 2010 11:23:57 AM CDT
bash-3.00# zfs listHey! That's exciting! It did EXACTLY as I thought - it destroyed the new filesystem I created. What was once 41G is now 78k. ;-( But hang on, let's see what we end up with. Some time later...
NAME USED AVAIL REFER MOUNTPOINT
newmail 4.39G 263G 44.0K /newmail
newmail/store 4.39G 263G 4.39G /newmail/store
store 41.4G 292G 41.2G /store
store@today 78.0K - 41.0G -
store@L8R 193M - 41.2G -
bash-3.00# zfs list && date7GB?! I only added about 200MB to the original so this is interesting ... Wait a bit more ...
NAME USED AVAIL REFER MOUNTPOINT
newmail 7.02G 260G 44.0K /newmail
newmail/store 7.02G 260G 7.02G /newmail/store
store 41.4G 292G 41.2G /store
store@today 78.0K - 41.0G -
store@L8R 193M - 41.2G -
Friday, June 11, 2010 11:29:47 AM CDT
bash-3.00# zfs list && dateOkay - that is WAY bigger than the snapshot. Interesting... Wait a bit more ...
NAME USED AVAIL REFER MOUNTPOINT
newmail 18.1G 249G 44.0K /newmail
newmail/store 18.1G 249G 18.1G /newmail/store
store 41.4G 292G 41.2G /store
store@today 78.0K - 41.0G -
store@L8R 193M - 41.2G -
Friday, June 11, 2010 11:35:15 AM CDT
bash-3.00# zfs list && dateOkay, it is definitely going to recreate the entire 41GB and (hopefully) include the extra stuff I added. Exactly what I expected BUT I'll take it.
NAME USED AVAIL REFER MOUNTPOINT
newmail 38.4G 229G 44.0K /newmail
newmail/store 38.4G 229G 38.4G /newmail/store
store 41.4G 292G 41.2G /store
store@today 78.0K - 41.0G -
store@L8R 193M - 41.2G -
Friday, June 11, 2010 11:44:58 AM CDT
A few minutes later - TA-DAHHH! It is done. It took 23 minutes (the first time it took 20-21 minutes). Weird. I don't see the point of the 2nd snapshot - just stop and snapshot the first time - or, I've done something wrong (most likely).
Oh well. Fun experiment. But I'd better do some more reading before trying this live. Incidentally, this Solaris 10 ZFS Essentials
is really nice for those times you're away from a PC and want to read about ZFS. I haven't seen the new Solaris ZFS Administration Guide
but I'm putting it on my list of books to acquire.Hopefully, this was useful or at least entertaining. I know, I know! "RTFM!" (Which stands for Read the Fine Manual, of course).
