[Gllug] Hardware recommendation, esp. SANs and shared storage

[Simon Trimmer]

On Thu, 8 Aug 2002, Matthew Kirkwood wrote:
> There was some discussion on this list a while back about
> external storage.  Someone mentioned a company based in
> Wimbledon who do beige-box fibrechannel storage, but I
> can't find it in the archive.  We need at least a terabyte
> available (probably in a mix of RAID 5 and 0+1), ideally
> in a chassis with room to double that.

SANs, where do I start....

Think long and hard about buying noname fibre channel kit, hardware from the
big players has trouble talking to each other let alone trying to get a
working rig on the cheap! :)

Applying raid at the array level is pricey, so I havn't looked in that
direction, but you certainly want raid somewhere as disks fail scarily often.
I don't know how oracle handles it's devices, so look into volume management
to handle the fabric moving around underneath you. I'm a free agent now so
use whichever lvm you want to bet your business on.

There are fairly good JBOD cabinets out there, you're talking about £10,000
for an eight to ten slot chassis loaded with 18GB 10k rpm FC disks.  If you
can screw 36GB disks out of them you're doing very well :)

You're probably going to just get away with it, but be aware that if you have
more than 40 scsi disks with redhat you're probably going to need to
recompile the kernel with more sd extra devs and this might have support
implications.

Fibre channel cards.  Overall, the best cards I've used are the QLogic 22xx
and 23xx series. There are plenty of fully open source drivers (including
their own) and the performance is extremely good. Don't be fooled by the
source emulex driver, it builds wrappers and links against a binary core.

And, for the future be aware of 1 TB and 2 TB addressing limitations of some
linux filesystems and block devices and that you're not going to get more
than 128 disks on a linux machine without some Hacking.


> Similarly, anyone have experience with new, chunky (4-8
> CPUs, 4-16Gb RAM) hardware from the usual Big Names?  It
> looks like Dell offer the best bang per buck, and with
> pretty current hardware, but two of our guys have horror
> stories about Dell support.

If you deal with any company long enough you're going to get horror story
situations :)

Most of my big kit is Dell, I have found it to be well built and pretty
reliable under extreme load (the Dell engineer had a heart attack when I
showed him the 8way running at 100% load on all cpus).

You can get the service manuals off the Dell web site and with their
openmanage software you can read the hardware management log / run hardware
diagnostics on the fly. (The ESM log is essential reading, the backplane is
quite clever you get plenty of warnings before the shit actually hits the
fan)

If you can diagnose hardware faults and bully them into giving you what you
want you won't have much trouble with dell support, they have different
levels of people so you have to work their system to get to the best
engineers.

We had a couple of compaq boxes, they can have some wierd array hardware but
I think we got them working well enough. They aren't here anymore.


> - currently trying to convince Oracle reseller that
>   a 4-way P4 with hyperthreading is only 4 CPUs for
>   licencing purposes :-)

P4 hyperthreading doesn't always make things go faster, trial and benchmark
your apps properly to load failure...it's nice you have a couple more engines
but as they share a lot of the core you might find it's not worth the hassle
and can make things go slower.


Glossed over a lot of technology in there huh? :)

-Simon
Simon Trimmer <simon at urbanmyth.org>





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