John R. Dunning wrote:
I'm getting my first exposure to a ddn storage array and it's enlightening :-}
Mostly it just does what I expected of it with little trouble, but I'm having
hard time getting the read side working as fast as it ought to be able to go.
Does anybody have experience they'd like to share, tuning the kernel/driver or
the array?
I'm using 2.6.15 kernel, and qlogic 2462 hbas with 8.01.07 driver. Using the
anticipatory scheduler, and tweaking up the readahead size for the blockdev, I
can get around 300MB/s by using 4 threads on a port, or about 3/4 of the
expected max. Writes max out easily. The ddn's stats say that the large
majority of my reads are only 256K, even though the requests are larger than
that.
I tried incorporating the blkdev-max-io-size-selection and
increase-sglist-size patches from cfs, but that didn't really help, my reads
are still maxing out at 256K.
If anybody's been through this kind of thing and has experiences, rumors, or
war stories about what kinds of tuning in this area yield good results, I'd
love to talk to you!
I know this won't help you but for posterities sake use IBGD 1.8.2 if
you have an infiniband DDN array. I tried for 4 days with OFED 1.1.1 to
get decent io performance and never could. 30 minutes to install IBGD
and I was pushing 700MB/sec through the port using dd.
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