[Beowulf] Software RAID?

Joe Landman landman at scalableinformatics.com
Thu Nov 22 09:37:30 EST 2007


Jim Lux wrote:

>> If you can afford SCSI drives, why not buy a great raidcard as well?
> 
> What if your raid card fails, and the mfr no longer is in business? 
> You'd have to do some intelligent sparing of raid controllers, too.

A good vendor will have a few extra of these in stock.  We have seen 
motherboard companies come and go, and this has impacted users. 
Especially when they have some not-too-popular features like HTX 
connectors, and you can't get replacements that will fit the box form 
factor.

This is not (unfortunately) a theoretical point (unlike the RAID card 
issue), this did happen to us.

We have seen tape drive manufacturers refuse to sell users replacement 
drives for failed tape drives, as they wanted to sell their new stuff. 
Which does a customer with years of data backed up on the old system no 
good.

Its not just "if they go out of business", its "if they decide not to 
sell/support this anymore" which is a wider case.

This is why, if you do get one of those horrible proprietary solutions ( 
:^ ), you need to insist on some amount of parts depot, including the 
horrible proprietary cards.  This is an insurance policy against 
failure.  Then again, so is RAID1 (replication, where you pay twice as 
much for your drive space).

The issue of a vendor turning something into a brick does happen.  The 
idea is to guard against the risk by choosing/preferring open hardware 
whereever possible.  Even if the vendor ceases production/sales/support, 
you have a fighting chance of continuing support for as long as you wish 
it.  In the OFED package, we see support for the Amasso 1100 cards. 
Amasso went out of business several years ago.  Their cards are iWARP 
card, with TOEs, and other bits.  Despite many protestations to the 
contrary, these cards did a great job on MPI.  These days, the Myrinet 
and IB cards are about the same price as the Amasso cards, though the 
switches are a little more.

This is BTW one of the things I like about Myricom.  Their new cards do 
a nice job on 10GbE, put one into a unit yesterday, and it took me 2 
minutes to install the driver and make it work.  It is 10 GbE. 
Something happens, we have source code, and there are cards we can depot 
stock.  Same with the "horrible proprietary RAID vendors".

I guess I find it amusing that people warn against the "horrible 
proprietary hardware vendors" while happily expounding upon the usage of 
a proprietary software package :)  Either company goes away, you have an 
expensive brick/frisbee.  Its hard to get license changes/updates from a 
company that is out of business.

More to the point, if you are going to build a business case, it is very 
important to ask "how do I handle X".  Proprietary is not evil in and of 
itself.  Proprietary without a plan to deal with the "what happens if" 
issues is dangerous.  But then again, open hardware/software without 
such a plan is also dangerous ... would cost you downtime and effort.

Joe

-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://www.scalableinformatics.com
        http://jackrabbit.scalableinformatics.com
phone: +1 734 786 8423
fax  : +1 866 888 3112
cell : +1 734 612 4615
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