David Pcolar david_pcolar at unc.edu
Tue Jul 18 12:37:58 EDT 2006

On Jul 18, 2006, at 10:32 AM, Matt Pusateri wrote:
>> Hello Triluger's,
>> I've been tasked with finding our company a SAN.  Currently we've
>> looked at EMC & Lefthandnetworks.  Were leaning towards ISCSI,

There are several questions that come to mind immediately:

What I/O load profiles are you planning to put on the SAN?
What about the number of LUNs?
Will the iSCSI mounts be across a WAN?  If so, are you planning to 
tunnel them?
Are you planning to boot from the SAN?
Are the LUNs to be mounted directly in the *nix environment or will they 
be PVs in a LVM setup?
Will your backups be done from the mount point or via NDMP from the 
iSCSI box?
Do you have Jumbo Packet support on your links?
Dedicated NICs on the end points or shared?

I'm sure you  thought this through, but remember 1 LUN = 1 mount point.  
There's no LUN sharing - especially in a Win environment.
Openfiler is OK, but the iSCSI reliability and performance is not robust. 
Look closely at what the iSCSI box can support in terms of simultaneous 
connections and LUNs exported.  I don't know of any boxes which natively 
support tunneling or other encryption.

If you are planning to support web serving of the content or other high 
IO activities, think about the net propagation delays inherent with iSCSI. 

My experience with iSCSI is mixed.  It is a great way to add flexible 
storage - especially for Win systems.  IO performance has a lot of 
variability - unless you are engineering and monitoring the connections 
end-to-end.  Don't let all of this scare you away or drive you to 
vendors that gloss over the details.  Engineering the solution for your 
current load and 2 years out will tell you if this will really work.  If 
you do go with a big vendor, ask for a demo over your network...

Hope it helps,

Dave Pcolar

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