Re: cgd + zfs

[David Brownlee <abs%absd.org@localhost>]

On Wed, 14 Jul 2021 at 06:13, Pouya Tafti <pouya+lists.9fans%nohup.io@localhost> wrote:
>
> (Apologies in case this is not the right mailing list.)
>
> *tl;dr* Is it sensible to use zfs on top of cgd or are there drawbacks w.r.t. zfs expecting raw I/O?
>
> (Too many) details follow.
>
> I plan to re-purpose a circa 2012 Supermicro server for a cheap home NAS.  It comes with an LSI MegaRAID 9261-8i controller and 8x 1TB SAS HDDs.  I'm wondering--without any experience with zfs--whether it may be more flexible/future-proof than RAID, and am considering using it instead (undecided yet as to the optimal configuration but I'm thinking a pool of 2x sets in RAIDZ2 may be sensible, so I can replace a single set with bigger HDDs later on if I need to).

Depending on your upgrade plans you may want to consider one 6x1TB
RAIDZ2 rather than 2 4x1TB RAIDZ2 - you end up with the same amount of
usable space and you have two spare bays for when the time comes to
upgrade. (This suggestion is much relevant if you have other systems
where you can easily hook up a 4 drive RAIDZ2, but not a 6 drive
RAIDZ2 :-p)

I have a somewhat similar setup on a Dell T320 - SAS9217-8i with 8
drives (plus one on onboard ahcisata), 6 in a RAIDZ2, two in a zfs
mirror and one for boot

zfs is setup to use wedges via /dev/wedges and then adjusted
rc.d/devpubd to run _before_ zfs, so I have stable zfs devices if
anything renumbers on reboot

ls -l /dev/wedges
total 0
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 backup0 -> /dev/dk0
lrwxr-xr-x  1 root  wheel  9 Jun 12 05:40 backup1 -> /dev/dk11
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 efi1 -> /dev/dk7
lrwxr-xr-x  1 root  wheel  9 Jun 12 05:40 home1 -> /dev/dk10
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 media0 -> /dev/dk1
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 media1 -> /dev/dk2
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 media2 -> /dev/dk3
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 media3 -> /dev/dk4
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 media4 -> /dev/dk5
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 media5 -> /dev/dk6
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 root1 -> /dev/dk8
lrwxr-xr-x  1 root  wheel  8 Jun 12 05:40 swap1 -> /dev/dk9


David