Yes, it's enterprise -- a pair of HP EVA arrays. We're talking to them via
4Gb fibre-channel. Single-initiator zones. There's a combination of RAID
levels going on on the arrays.... but it all used to perform so *well*.
The connection goes like this
EVA -->
(4Gb FC) -->
Windows Backup Proxy Server -->
(1Gb Eth, TCP port 1500) -->
Windows Backup Server (TSM)
This is a combination that had worked very well for us, until we "upgraded"
from a pair of 4Gb Brocade switches to four 8Gb Qlogic switches. I can't
downgrade back to the Brocades, unfortunately, but may do a sideways back
to a new set of 8Gb Brocades if this silliness can't be resolved.
The Proxy server has a Qlogic HBA, so at this point... having twiddled just
about every lever and dial available (I've even went off the deep end and
started altering the maximum data transfer size, FC frame sizing, etc.)
I'm starting to think this Qlogic HBA is trying to be clever with it's
Qlogic switch and am going to order an Emulex HBA to see if I'm right.
Thanks for provoking thought, if nothing else :)
Mike
On Fri, Feb 7, 2014 at 7:07 AM, Edward Ned Harvey (lopser) <
lop...@nedharvey.com> wrote:
> Ok - I don't think it's been clear, what you have connected to where, and
> what type of storage (or what type of storage operation) you're trying to
> do...
>
> You have some kind of storage - presumably enterprise grade SAN storage
> array, with hardware raid controller, in raid6 I guess? It is attached via
> the aforementioned redundant FC network, to some backup server, with
> redundant HBA's. Right? And it's all single initiator, so there is no
> competition from other initiators competing for storage performance. Right?
>
> The backup server is connected via 1Gb ether, to some other servers.
> You're pushing backups from those other servers, across the ether, and
> ultimately onto the SAN storage. Since the FC is supposed to be much
> faster than the 1GB ether, you would expect the ether to be the bottleneck.
> 800 Mbit is suboptimal, but kind of close to acceptable... So it's weird
> to be encountering this limit around 350 Mbit. Weirder still, on the
> backup server, you toggle the dominance of the HBA's, the performance
> suddenly jumps to 800Mbit, but only temporarily.
>
> Have I got all that right?
>
> So...
>
> What protocol are you talking over the ethernet? Because some protocols,
> such as iscsi, would very likely perform blocking writes, waiting for data
> to flush out to disk - In which case, the SAN configuration and raid
> configuration could truly make a big difference. You would want to make
> sure you have some sort of write-back cache enabled. Also, supposing you
> have raid5 or 6 or similar, if you're doing any sort of random IO (rather
> than a single sustained sequential stream) then raid5 or 6 or similar would
> very likely perform poorly, which could hit you if your job is waiting for
> buffer flushes out to disk.
>
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