Gary Mills wrote:
On Fri, Dec 14, 2007 at 10:55:10PM -0800, Jonathan Loran wrote:
This is the same configuration we use on 4 separate servers (T2000, two
X4100, and a V215). We do use a different iSCSI solution, but we have
the same multi path config setup with scsi_vhci. Dual GigE switches on
separate NICs both server and iSCSI node side. We suffered from the
e1000g interface flapping bug, on two of these systems, and one time a
SAN interface went down to stay (until reboot). The vhci multi path
performed flawlessly. I scrubbed the pools (one of them is 10TB) and no
errors were found, even though we had heavy IO at the time of the NIC
failure. I think this configuration is a good one.
Thanks for the response. I did a failover test by disconnecting
ethernet cables yesterday. It didn't behave the way it was supposed
to. Likely there's something wrong with my multipath configuration.
I'll have to review it, but that's why I have a test server.
I was concerned about simultaneous SCSI commands over the two paths
that might get executed out of order, but something must ensure that
that never happens.
From the Sun side, the scsi_vhci is pretty simple. There's a number of
options you can tweak with mdadm, but I haven't ever needed to. Perhaps
you will however. The iSCSI targets may be persisting on the failed
path for some reason, I don't now. Not familiar with the Netapp in
iSCSI config. Our targets simply respond on what ever path a SCSI
command is sent on. This means the initiator side (scsi_vhci) drives
the path assignments for each iSCSI command. At least this is how I
understand it. The scsi_vhci will never send two of the same commands
to both paths, as long as they are up. If a paths fails, then a retry
of any pending operations will occur on the operational path, and that's
it. If a path returns to service, then it will be re-utilized.
Jon
--
- _____/ _____/ / - Jonathan Loran - -
- / / / IT Manager -
- _____ / _____ / / Space Sciences Laboratory, UC Berkeley
- / / / (510) 643-5146 [EMAIL PROTECTED]
- ______/ ______/ ______/ AST:7731^29u18e3
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