[Beowulf] GPFS on Linux (x86)
hahn at physics.mcmaster.ca
Thu Sep 14 19:44:56 EDT 2006
> work ok. They describe it as the SATA disks go 'out to lunch' occasionally
> and a disk will have a large pause before continuing. Those comments come
> from a vendor (Be wary).
this is true, sorta. it wasn't really a big surprise - most of the
initial generation of SATA disks were designed for non-24x7 workloads,
and if you actually kept them busy for a couple hundred hours, they'd
take a vacation, like it or not. it didn't help that Linux's MD raid
was intentionally naive about handling this kind of error.
I'm pretty sure I remember some older SCSI disks having that problem too.
but there are obvious fixes, and vendors know about this and treat
it as a marketing feature, so everyone's happy ;)
(personally, I don't often have SATA disks in raid which are actually
busy all the time. but we're an academic HPC site, so don't have
anything like 24x7 DB activity, or CERN-like streams of data...)
> But if my customer wants 15K disks, I am going to get them for him/her.
> I am not going put the effort in convincing them to go with SATA. You
> pick your battles even when serving them.
I'm thankful that in most ways, I'm a customer, not on the other side ;)
but it's worthwhile to note that SCSI disks are still dramatically
more expensive than SATA. yes, there are reasons, but even so,
price/performance is a pretty strong argument...
> Large SATA array vs. Large SCSI array, same vendor. It appears that the
> SCSI disks were a bit more reliable. I wish I had more numbers to back it
> up, but that is what it seemed like. I don't buy any of the vendor
well, for what it's worth, my organization bought something like 6k
SATA disks over the past year, and have seen pretty sparse failures.
(unfortunately, our book-keeping is probably not good enough...)
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