[CentOS] iSCSI best practices

Fri Dec 9 17:02:11 UTC 2011
Adam Wead <amsterdamos at gmail.com>

On Fri, Dec 9, 2011 at 11:27 AM, Alan McKay <alan.mckay at gmail.com> wrote

> So 2 questions :
> - how important is it to have it on its own network?

I would say very important, but probably not required.  A separate network
segregates the traffic, and you can secure it better.  You can also have
failover, etc, and potentially use cheaper switches.

> - is it OK to use an unmanaged switch (as long as it is Gigabit), or are
> there some features of a managed switch that are desirable/required with
> iSCSI?

I've setup two iSCSI storage networks.  The first was with unmanaged Dell
switches... each was only about $200 I think, and it worked great.  For the
second, I'm not using switches at all and connecting directly from the NIC
on the server to the NIC on the disk array.  Fortunately, we only have a
couple of servers and the IBM disk array comes with an additional card that
has 4 NICs on it.

You can use managed switches, even ones that are currently supporting your
LAN, but I would create some VLANs to separate the traffic.  You should
also make sure jumbo frames are enabled as well.  If you're concerned about
maximizing throughput, then a managed switch will have more options to
fine-tune this such as link aggregation, but in my cases, I wasn't worried
about this because the "default" setup was fast enough for our needs.

In the current direct connect setup, the iSCSI network is supporting
virtual machines.  So even without much tinkering, the speed is good
enough.  However, everyone's requirements are different.

Adam Wead
Systems and Digital Collections Librarian
Rock and Roll Hall of Fame and Museum