Moving to ZFS

[Business_woman]

Hi,

I finally decided to try ZFS. I had an unused hard drive lying around, so i quickly wiped it and created a new ZFS pool. My old harddrive is still UFS though.
Can i use dump to move the contents of the entire UFS disk to the ZFS one?

I was also considering striping between the two disks

/Your beloved Business_Woman

[phoenix]

Yes, and no.

There are two methods to using ZFS:
* everything on ZFS with UFS /boot, or
* everything but / on ZFS

The second option is easier, and allows you to boot to single-user mode and use /rescue/* when needed.

A nice and easy setup if your system can boot off USB flash drives is to copy / (not /usr, /var, /tmp, or /home) onto the flash drive, use fdisk -B /dev/da0 (or whichever device it shows as) to make it bootable, then boot off it into single-user mode.

At that point, you can configure the ZFS pool and create filesystems for /usr, /var, /home, and so on and set their mountpoints. Then copy (find|cpio, or dump|restore) the data from the UFS harddrive to the ZFS filesystems.

Reboot using the ZFS harddrive to make sure everything still works correctly. Finally, add the UFS harddrive to the ZFS pool. Voila! A system that boots of UFS and stores everything volatile on ZFS.

[Business_woman]

hmm, so booting directly from ZFS won't work then?

[phoenix]

Nope. And there probably never will be.

[corey_james]

As phoenix has mentioned on several other threads - ZFS is experimental !

I have noticed a HUGE performance hit having /usr on ZFS but i think that's mostly due to lack of resources ( need more RAM )

[phoenix]

If you have a 64-bit system with lots of RAM (8+ GB) and CPU (4+ cores), ZFS is amazing!! Especially as a file server and backup server.

If you have a 64-bit system with adequate RAM (4+ GB) and CPU (2+ cores), ZFS is still very nice. Just depends on the load you put on it. We could lock up a system using 2x Opteron 200 CPUs and 8 GB DDR1 RAM by running 10+ simultaneous rsyncs. Same harddrives in a system with 2x Opteron 2200 CPUs and 8 GB DDR2 RAM doesn't flinch when running 40+ simultaneous rsyncs.

If you have a 32-bit system with 2-4 GB of RAM and a 2 GHz CPU, you can get decent performance out of ZFS by maxing out the kmem and tuning the ARC. But it can take a lot of fiddling and time to get it to a nice setup. Took me about a month to get the right values for my system (2 GB RAM). Haven't noticed any issues that are directly related to ZFS.

If you have a 32-bit system with less than 2 GB of RAM or 2 GHz CPU, don't bother with ZFS.

[tano]

I have two small kids at home who like hitting the reset button...

ZFS has kept my file system sane... AMD64 2800+ 512MB RAM, very low workload, works wonderfully (journalling is just great).

The only problem I had was compiling GHC to use xmonad (must have run low on memory)!!
Just did a pkg_add and presto...

BTW - Did I mention Xmonad absolutely rocks??!!