On 09/29/2015 04:56 PM, J David wrote:
On Thu, Sep 3, 2015 at 3:49 PM, Gurvinder Singh
<gurvindersinghdahiya@xxxxxxxxx> wrote:
The density would be higher than the 36 drive units but lower than the
72 drive units (though with shorter rack depth afaik).
You mean the 1U solution with 12 disk is longer in length than 72 disk
4U version ?
This is a bit old and I apologize for dredging it up, but I wanted to
weigh in that we have used a couple of the 6017R-73THDP+ 12 x 3.5" 1U
chassis and will not be using any more. The depth is truly obscene;
the 36" is not a misprint. If you have open racks they may be
acceptable but in a cabinet they are so long that they have to
mismount (sticking past the rack both front and rear) to close the
doors and in doing so, occlude so much space they raise concerns about
cabinet airflow.
They are also *very* cut down to get that many drives into the space.
They don't even have a physical serial port for console; they depend
entirely on IPMI for management. (And we have had very mixed success
with SuperMicro IPMI virtual serial consoles.) Also of course there
is no drive servicing done without shutting down the entire node,
making a simple drive swap vastly more labor intensive. If (as in our
case) the cluster is overprovisioned enough to survive the long-term
loss of several drives per unit until it makes sense to take the whole
thing down and replace them all it may be OK. In any situation where
you expect most/all platters to be spinning, they're a non-start.
All in all, the money / rack units saved is not even close to worth
the extra hassle involved, particularly when you start counting up how
many of those 12 drives you are treating as spares to space out
servicing it.
The 5018A-AR12L looks like a better layout that trims down to a
"svelte" 32" of depth, but appears to keep most of the rest of the
downsides of its 36" cousin. That wired-in Atom processor also raises
some concerns about CPU overload during any major OSD rebalance.
FWIW, I've mentioned to Supermicro that I would *really* love a version
of the 5018A-AR12L that replaced the Atom with an embedded Xeon-D 1540. :)
Anyway, sorry for raising an old issue, but if I can save even one
person from going with these for Ceph, it was worth it.
I think any time you start talking really high density, you have to talk
trade-offs. The 72 drive chassis is around the same depth as the 6017R,
and while drive replacement is easier (though you still have to take 2
OSDs down at once), there are plenty of other areas where you have to
make fairly significant compromises. I think the 6017Rs are still worth
considering so long as you know that they aren't really hotswap-drive
capable. They will probably work best in an environment where you can
either leave broken OSDs down for a while or swap out entire nodes at
once (ie you need a lot of them).
For medium-large sized deployments, the SC847 chassis is probably a
fairly reasonable as a compromise despite it's age. 36 bays in 4U,
27.5" depth, all drives hotswap, lots of PCIe expandability, cheap
price. I still maintain that you want at least a rack (~10) of them
though. As always the more nodes you can spread failures over the better.
Thanks!
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