How to dump / restore entire Dataset

[Hans Baumeister]

Hi, I set up a RAIDZ1 on three 3GB drives (on 9.2.2) last week, not realizing that you couldn't expand the dataset of a RAIDZ1 after creating it (at least not with one drive). Now that I've RTFM, I realize that in order to add the 4th drive, I'll need to re-do the dataset.

I've already copied quite a bit of data onto it and set up ownCloud in a jail. Sure, I can re-do all of that, but perhaps there is an easier way? Being the Noob that I am, I'm thinking along the lines of dumping (dd?) the entire ZFS dataset onto an externally attached drive, then re-creating the dataset with 4 drives and dumping the ZFS dataset back onto the FreeNAS.

Is something like that possible? I've tried to find an answer to that but so far no luck.

Thanks!

 

[Sir.Robin]

You want to recreate the volume wich the Dataset resides on.

That said, yes, you can do what you are asking.

I did this myself, although not with an external HDD. I used 4 drives and created a temp raidz2.

Stop any services using the dataset.
Crate a snapshot of your dataset.
Create a temp volume on secondary drive(s) then replicate your dataset to this.
Destroy and recreate the volume on your primary drives.
Then replicate the dataset back.

Code:

zfs send volume/dataset@snap1 | zfs recv tempvolume/dataset

 

[Hans Baumeister]

Cool, thanks Sir Robin; my additional Disk should be here tomorrow, I'll give it a shot.
I presume it should work if tempvolume is a single disk as well.
I'll post when I succeed/fail.

 

[Hans Baumeister]

Okay, I've got some results, but they aren't very good.
First of all, I needed some additional switches in both the send and receive commands. First of all, a "-r" to send recursively and then a "-rF" to receive recursively and force a write to the volume.
The transfer seemed to work, when I autoimported Temp, I was able to see all the datasets I had created and snapshotted.

Unfortunately, when I tried doing the reverse (after forcing a snapshot on Temp), even though the transfer back took hours, it apparently didn't transfer everything.

I ended up rebuilding the FreeNAS with the 4th drive installed (completely from scratch) and then using a regular cp command from the autoimported Temp volume to transfer the contents of each individual dataset to the new volume on the newly created NAS:

cp -iprv /mnt/Temp/Dataset1 /mnt/FinalData/Dataset1/

(the destination volume and dataset names are fictitious, of course).

Here are what the switches stand for:


i = Interactive. Will prompt you if overwriting files.
p = Preserve file attributes like date, time, etc.
r = Recursive. Will also copy subdirectories.
v = Verbose. Will show each file as it is copied.

 

[Sir.Robin]

If you have several datasets, you need to do a recursive snapshot. Or, one snap/zfs send for each dataset.

I did a recursive snapshot on the volume. Chceking you will then see all datasets have a snapshot with the same name.
Then i did a recursive send vol@snap1.

Done this several times and had no issues.

Not sure why you needed force to send back... didn't you recreate the volume? as in empty?

 

[Hans Baumeister]

Yep - recursive snapshot on the volume was done and I also saw that it generated a snapshot for each data set - so far so good. Why it didn't work the way I expected I'll probably never know. Thanks anyways!