[Beowulf] Software Raid

Gerry Creager N5JXS gerry.creager at tamu.edu
Fri Dec 16 06:18:54 PST 2005

Sean Dilda wrote:
> Chris Samuel wrote:
>> On Thursday 15 December 2005 01:29, Sean Dilda wrote:
>>> However, as I understand it, most hardware raid is handled by 
>>> firmware on
>>> the hardware.  And even if it isn't, the chips that do the work are of
>>> relatively new design. 
>> Not necessarily true, often the "consumer end" ATA RAID cards are 
>> really fakeraid, where some portion of the work is offloaded to the 
>> driver to do.  Kind of like the endless pain that is winmodems.
> I'm aware of those.  I think we can safely say that those are not 
> Hardware RAID :)  They're just software raid which requires special 
> hardware, which means its the worse of all the options.

What's discouraging is that while there's now good (or at least better) 
documentation on these, some of us spent a lot of time, money, effort 
and reputation learning about fakeraid.

Then, there's the 3Wares of the world.  When we determined the Promise 
"solution" wasn't working for our NexRAD radar cache system, we went to 
the 7506 series 3Ware, and still had problems.  A call to tech support, 
telling them the issue appeared to be worse with the 2.6 kernel, saw a 
couple of new 9506-12 controllers in our hands by overnight shipment. 
Free.  As in beer.  And a follow-up call to make sure things were better 
  (and, yes, they were/are).

One other consideration now:  The hard disk vendors are finally coming 
out with higher speed, and higher reliability SATA drives than the 
cheaper consumer-grade stuff.  We're aging out our consumer-grade SATA 
drives in our RAID in favor of the new hardware.

Finally:  ATA-over-Ethernet...

We have now invested in 26TB of AoE hardware, getting the CoRAID 
shelves.  We've got 3 months on the firsg 6 TB and are very happy with 
performance and reliability.  And, yes, Virginia, it does do RAID 
5/50... or 0/1/10 or almost anywhere in between.

Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843

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