[Lustre-discuss] RAID cards - what works well with Lustre?

[Daire Byrne]

Hi,

I have been testing some LSI 9260 RAID cards for use with Lustre v1.8.6 but
have found that the "megaraid_sas" driver is not really able to facilitate
the 1MB full stripe IOs that Lustre likes. This topic has also come up
recently in the following two email threads:

http://groups.google.com/group/lustre-discuss-list/browse_thread/thread/65a1fdc312b0eccb#
http://groups.google.com/group/lustre-discuss-list/browse_thread/thread/fcf39d85b7e945ab

I was able to up the max_hw_sectors_kb -> 1024 by setting the "max_sectors"
megaraid_sas module option but found that the IOs were still being pretty
fragmented:

disk I/O size          ios   % cum % |  ios   % cum %
4K:                   3060   0   0   | 2611   0   0
8K:                   3261   0   0   | 2664   0   0
16K:                  6408   0   1   | 5296   0   1
32K:                 13025   1   2   | 10692   1   2
64K:                 48397   4   6   | 26417   2   4
128K:                50166   4  10   | 42218   4   9
256K:               113124   9  20   | 86516   8  17
512K:               677242  57  78   | 448231  45  63
1M:                 254195  21 100   | 355804  36 100

So next I looked at the sg_tablesize and found it was being set to "80" by
the driver (which queries the firmware). I tried to hack the driver and
increase this value but bad things happened and so it looks like it is a
genuine hardware limit with these cards.

The overall throughput isn't exactly terrible because the
RAID write-back cache does a reasonable job but I suspect it could be
better, e.g.

ost  3 sz 201326592K rsz 1024K obj  192 thr  192 write 1100.52 [ 231.75,
529.96] read  940.26 [ 275.70, 357.60]
ost  3 sz 201326592K rsz 1024K obj  192 thr  384 write 1112.19 [ 184.80,
546.43] read 1169.20 [ 337.63, 462.52]
ost  3 sz 201326592K rsz 1024K obj  192 thr  768 write 1217.79 [ 219.77,
665.32] read 1532.47 [ 403.58, 552.43]
ost  3 sz 201326592K rsz 1024K obj  384 thr  384 write  920.87 [ 171.82,
466.77] read  901.03 [ 257.73, 372.87]
ost  3 sz 201326592K rsz 1024K obj  384 thr  768 write 1058.11 [ 166.83,
681.25] read 1309.63 [ 346.64, 484.51]

All of this brings me to my main question - what internal cards have people
here used which work well with Lustre?  3ware, Areca or other models of LSI?

Cheers,

Daire
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