ZFS on Hardware RAID

[Freddie Cash]

On Sun, Jan 20, 2019, 12:09 PM jdelisle <jdelisle at gmail.com wrote:

> On Sun, Jan 20, 2019 at 9:04 AM andy thomas <andy at time-domain.co.uk>
> wrote:
>
> > I don't h/w RAID controllers do any parity checking, etc for RAID 0
> > virtual disks containing only one disk?
> >
>
> I can say for certain that with Dell PERC 6/e RAID (SAS 8087ELP based)
> cards, when the virtual devices are entire disks each in a RAID0
> configuration, the way the adapter writes data to them is effectively the
> same as JBOD.  You can take a RAID0 drive from a PERC 6/e controller and
> use in with an HBA/ "IT Mode" JBOD controller without issue.  I personally
> migrated 14x 1TB drives off PERC 6/e (all RAID0's) to a SAS 6gbps HBA, and
> my ZFS VDEV's and pools were totally fine.  You can move back and forth no
> problem.  I can't say this is the case for ALL RAID controllers, I've only
> done this with an old PERC 6/e.


3Ware controllers configured for Single Disk arrays (which is different
from JBOD mode) work the same way. You can move a disk from a Single Disk
setup to a software RAID (mdadm or ZFS) without issue. We've migrated many
Linux and FreeBSD systems from 3Ware to HBA to onboard SATA at work.

I believe the difference between Single and JBOD on the 3Ware is the former
allows the onboard cache to be used.

Cheers,
Freddie

Typos due to smartphone keyboard.