Okay, I think there's been enough interest expressed that I'm just
going to send this to the list, even though this is more about disk
products than AFS.
MIT is also in the process of evaluating RAID products for use in our
central AFS cell (athena.mit.edu). I'm one of the people working on
the evaluation. We're looking at 36-40 GB (usable space) arrays,
connected to some form of UltraSPARC (probably an Ultra 2 or an Ultra
5).
Since the evaluation is still happening, we don't have all the
information yet, but I can share what we do have.
Products currently under consideration:
SUN:
http://www.sun.com/storage/A1000/
RAID Array A1000. This hardware RAID was just released at the
end of April. We've been promised an eval unit by the end of this
week. It doesn't support disks larger than 4 GB, which is too bad in
some ways, but we're going to test it anyway.
http://www.sun.com/storage/multipack/
StorEdge MultiPack. A dumb box of SCSI disks, which allows
hot-swap of disks, and not much else. It would be used in conjunction
with a software RAID package, like Sun's Solstice DiskSuite. Even
with the additional disk space overhead of RAID 0+1 as opposed to RAID
5, this appears to be the most economical solution. Not terribly
featureful in the hardware (no hot-swap ability other than the disks
themselves), and I haven't had a chance to test the interaction
between Solstice and the AFS server software.
DEC:
http://www.storage.digital.com/menuproduct.htm
Dumb JBOD system, built around the BA356 shelf. Lots of
hot-swappable components, but quite expensive (comparable with some
hardware RAIDs). Like the Sun MultiPack, this would be used with a
software RAID package.
Western Scientific:
http://www.wsm.com/catalog/raid/ultra.htm
CycloneRAID Ultra 35. Hardware RAID, built around a
single-path CMD controller. Just finished up with our eval unit. I
liked a lot of the characteristics of this unit; it was economical
(for a hardware RAID), expandable, sturdy, and fast. Aside from a
Solaris SCSI driver bug (which we fixed by installing a patch from
Sun), there were no problems integrating it with an AFS server. There
are a couple issues with it. Unlike most hardware RAIDs on the
market, this array's cache memory is volatile. This means that if the
RAID loses power at the wrong moment, a lot of data and metadata can
get lost. (Of course, it turns out that if the OS also does disk
caching, it doesn't matter whether the RAID's cache loses, since the
machine's cache will lose.) The unit we evaled also had a firmware
bug which could leave the internal disks unusable. WS claims that's
been fixed.
Box Hill:
http://www.boxhill.com/products/storage/raidbox.html
RAID Box 5300 Turbo+. Hardware RAID, built around a dual-path
CMD controller. The paperwork to get an eval unit is in Purchasing
right now. From specs, it looks like this unit clears up a couple of
the issues that the WS unit has (non-volatile cache, dual-path
active-active controllers), but is a bit more expensive. However,
it's still cheaper than Sun and DEC.
ADS:
http://www.adsys.com/disc.html
CMD(?) RAID. This is a strange situation. When we first
queried ADS, they suggested that we buy a DEC unit through them.
When, upon further investigation, it was discovered that DEC didn't
have a RAID product that fit our needs, we went back to ADS and tried
again. They've said they could assemble something based around a CMD
controller to fit our needs, but we don't have exact specs or much of
any other information. Still looking into this one.
Products/vendors currently not under consideration:
DEC:
RAID Array RA3000. Hardware RAID, of the correct size.
Unfortunately for DEC's reputation as makers of good RAIDs, they don't
currently support the unit under any OS other than WinNT and possibly
DG/UX. According to our sales rep, it'll be qualified for other
Unixen around the middle of the summer, but that's too late for MIT's
purchasing purposes. Our rep is pushing the aforementioned
BA356-based JBOD product instead.
HP:
HP makes disk arrays, but they only work with HP/UX and WinNT,
and aren't sold except as part of an HP server package.
IBM:
They haven't returned our calls.
Artecon:
Our group has had problems with their service department in
the past, and doesn't do business with them.
So, that's about where things stand. It would be interesting to hear
if anyone has suggestions of other units that bear evaluating. It's
unfortunate that among the "large" hardware vendors, only Sun has a
hardware RAID that will work for us in the right timeframe. The
smaller commodity-disk vendors (like ADS, Box Hill, Western
Scientific, and the like) all seem to be building units based on CMD
controllers. I suspect that we won't see much variation in quality
and price among these units, so while we could eval a large number of
such units, it's probably not worth it. So far, we've looked at WS
and ADS because we've had positive dealings with them in the past, and
at Box Hill on recommendations as a solid, established vendor
(apparently they started out catering to Wall Street firms before
expanding).
I'd love to hear if anyone has more information on vendors or products
that we haven't considered yet, or news on RAIDs' interactions with
AFS server software.
If there's interest, I'll send more information when we've completed
more of our evaluations.
Mike Whitson
MIT/IS Athena Server Operations
