[CentOS] openfiler (was: using CentOS as an iSCSI server?)
John R Pierce
pierce at hogranch.com
Tue Oct 20 21:43:48 UTC 2009
absolutely CRITICAL to any SAN implementations is that the storage
controller (iscsi target, be it openfiler or what) remain 100% rock
solid tsable at all times.
you can NOT REboot a shared storage controller without shutting all
client systems down first (or at least unmounting all SAN volumes)
its non-trivial to implement a high availability (active/standby)
storage controller with iscsi. very hard, in fact.
commercial SANs are fully redundant, with redundant fiberchannel cards
on each client and storage controller, redundant fiberchannel switches,
redundant paths from the storage controllers to the actual drive arrays,
etc. many of them shadow the writeback cache storage so if one
controller fails the other one has any write cached blocks and can post
them to the disk spindles transparently to maintain complete data
coherency. Trying to achieve this level of 0.99999 uptime/reliability
with commodity hardware and software is not easy.
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