[Beowulf] hardware RAID versus mdadm versus LVM-striping

[Gerald Creager]

Hardware RAID, in my experience, works well with most LSI controllers 
(that haven't been modified to become Dell PERC controllers) and 3Ware 
controllers.  I've had pretty grim results with most others.  A 
colleague and I had great initial results with several ARECA 
controllers, but then they lost their minds and did strange things to 
our RAID'd volumes.  Different Linux distro's and no operator 
intervention at the times of failure, either.

Hardware RAID should use a real onboard controller and be real hardware 
RAID.  A lot of 'em use a "driver" which relies on the OS to actually do 
the RAID but with some proprietary bits that I don't know and can't see 
when they break.  In this case I'd rather use MD s/w RAID.  That said, 
if I can use a current 3Ware or LSI card (note caveat above; I've not 
had good performance with any PERC's) I'd rather do hardware RAID for 
simplicity and recoverability.

But, you have to do your own due diligence and know your hardware.

gerry

Alan Louis Scheinine wrote:
> I had a nightmare problem with a newly compiled kernel not booting.
> The problem may have been with the command mkblkdevs of nash but in
> any case I did extensive web search on the AHCI controller that I had
> in both a notebook and a desktop computer, both of which had the
> booting problem.
> 
> One example of the controller is
>    Intel ICH9M-E/M SATA AHCI Controller
> 
> In web postings there were many problems attributed to this controller.
> It does RAID 1 using software.  The Linux driver was (is?) a "work in 
> progress"
> from what I gather reading web postings.
> 
> Dr. A.J. Travis wrote:
>> The problem with using an on-board RAID controller is that many of
>  > these are 'host' RAID (i.e. need a Windows driver to do the RAID)
>  > in which case you are using the CPU anyway, and they also use
>  > proprietary formats.
> 
> My point is to underline this fact.  Hardware RAID 1 should be simple and
> reliable.  But when the RAID controller relies on software running on the
> O/S, then it might be better to use Linux software RAID.
> 
> Alan
> 

-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University
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