Wed Jun 22 18:38:05 UTC 2016
Chris Adams <linux at cmadams.net>

Once upon a time, John R Pierce <pierce at hogranch.com> said:
> of course, the really tricky problem is implementing an ISCSI
> storage infrastructure thats fully redundant and has no single point
> of failure.   this requires the redundant storage controllers to
> have shared write-back cache, fully redundant networking, etc.   The
> fiberchannel SAN folks had all this down pat 20 years ago, but at an
> astronomical price point.

Yep.  I inherited a home-brew iSCSI SAN with two CentOS servers and a
Dell MD3000 SAS storage array.  The servers run as a cluster, but you
don't get the benefits of specialized hardware.

We also have installed a few Dell EqualLogic iSCSI SANs.  They do have
the specialized hardware, like battery-backed caches and special
interconnects between the controllers.  They run active/standby, so they
can do "port mirroring" between controllers (where if port 1 on the
active controller loses link, but port 1 on the standby controller is
still up, the active controller can keep talking through the standby
controller's port).

I like the "build it yourself" approach for lots of things (sometimes
too many :) ), but IMHO you just can't reach the same level of HA and
performance as a dedicated SAN.

Chris Adams <linux at cmadams.net>