[zfs-discuss] Flash to IT mode after build

Andreas Dilger adilger at dilger.ca
Tue Apr 3 14:02:10 EDT 2018

On Apr 3, 2018, at 7:30 AM, dag dg <dagofthedofg at gmail.com> wrote:
> I have a ZFS storage pool already built, but it was done before I
> fully understood some of the finer details of HBAs and related RAID
> cards including the difference between IR mode firmware and IT mode
> firmware. I have 2 x LSI 9311-8i HBAs that are up and running my
> current ZFS pool that I believe came flashed with IR mode firmware.
> The disks are all set to JBOD I believe and appear to be getting
> passed through to the OS though I can't be sure.
> My concern at this point is whether I should flash the firmware over
> to IT mode or if that will cause more trouble that it's worth. In my
> performance tests so far my current state seems solid and stable but
> the fact that in my research I missed this kind of detail has me a bit
> uncertain of the long term outcome.
> Any insight would be appreciated.

There is some potential that changing the adapter firmware may cause the
devices to be labeled differently and skip a few sectors at the start when
presented to the OS (e.g. removing a RAID device label from the disk).

One way to check this non-destructively is to read the first few blocks
from the disk under your current configuration, then remove a disk and
install it in some non-RAID system and compare them, like:

    dd if=/dev/sdb bs=1M count=16 | sha1sum
    16777216 bytes transferred in 2.116622 secs (7926411 bytes/sec)
    bbed83e350470cc17e54b38e78f4b06687597184  -

You could also use md5sum or cksum if sha1sum is not installed.  If the
checksums are the same, then the "raw" device presentation is the same
as the "passthrough" device and it should "just work" after flashing the

Cheers, Andreas

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