[Beowulf] Any recommendations for a good JBOD?

[Rahul Nabar]

On Thu, Feb 18, 2010 at 1:55 PM, Alex Chekholko <chekh at pcbi.upenn.edu> wrote:
> On Thu, 18 Feb 2010 12:53:22 -0600
> Rahul Nabar <rpnabar at gmail.com> wrote:
>

>>
>> I was thinking SAS / SCSI / iSCSI is probably easiest and cheapest.

> Do you already have a suitable SAS or SCSI controller in the host
> machine?  If not, then you have to factor in the cost of the controller.

No. true. I have to factor in that price. But almost any kind of disk
array I can think of will need a controller, correct? Or are there any
JBOD formats that can be attached without putting in  a controller in
the server.

Are SAS  / SCSI controllers generic? Or are they paired to the JBOD
one buys? In the past I've only had hardware RAID so the card usually
came from te vendor that was selling the storage array. Also those
cards did RAID+Controller whereas this time I'll be shopping around
for a controller-only type of card since I want to do RAID via mdadm.

> If you want iSCSI, then you're looking at a low-end SAN as opposed to a
> DAS.  But the SAN/NAS distinction is blurry these days, as many devices
> can give you either block or file-level access.

Yes, true. I'm dropping iSCSC entirely. Don't have the $$ to do a SAN
with fibre switches etc.


>> > If performance is really not an issue, a consumer-level NAS box is
>> > probably your cheapest option.  A QNap TS-410 is ~$450 plus 4 x 2TB
>> > drives...
>>
>> Hmm...NAS. I was more thinking in terms of a DAS. Don't the NAS's come
>> with their own CPU's / RAM and stuff? (Like the Sun Thumper)
>
> Yes, they do.  But if you want to access 5TB via iSCSI (or NFS), that's
> likely the cheapest option.

That's quite non-intuitive to me. If it' a NAS they must need
procs+RAM+NICs on board. How does that get cheaper than an equivalent
"dumb" JBOD which outsources all these 3 functions to the attached
host server? Maybe I am missing a part of the argument.

I already have a server that the JBOD can be attached to so that cost
to me is a sunk cost. I just need to consider the incrementals above
that.

-- 
Rahul