You didn't say, but I think they are LSI-based: are you using the mptsas driver with the PERC cards? Which driver version?
First, max_sectors_kb should normally be set to a power of 2 number, like 256, over an odd size like 320. This number should also match the native raid size of the device, to avoid read-modify-write cycles. (See Bug 22886 on why not to make it > 1024 in general). See Bug 17086 for patches to increase the max_sectors_kb limitation for the mptsas driver to 1MB, or the true hardware maximum, rather than a driver limit; however, the hardware may still be limited to sizes < 1MB. Also, to clarify the sizes: the smallest bucket >= transfer_size is the one incremented, so a 320KB IO increments the 512KB bucket. Since your HW says it can only do a 320KB IO, there will never be a 1MB IO. You may want to instrument your HBA driver to see what is going on (ie, why the max_hw_sectors_kb is < 1024). Kevin Kevin Hildebrand wrote: > Hi, I'm having some performance issues on my Lustre filesystem and it > looks to me like it's related to I/Os getting fragmented before being > written to disk, but I can't figure out why. This system is RHEL5, > running Lustre 1.8.4. > > All of my OSTs look pretty much the same- > > read | write > pages per bulk r/w rpcs % cum % | rpcs % cum % > 1: 88811 38 38 | 46375 17 17 > 2: 1497 0 38 | 7733 2 20 > 4: 1161 0 39 | 1840 0 21 > 8: 1168 0 39 | 7148 2 24 > 16: 922 0 40 | 3297 1 25 > 32: 979 0 40 | 7602 2 28 > 64: 1576 0 41 | 9046 3 31 > 128: 7063 3 44 | 16284 6 37 > 256: 129282 55 100 | 162090 62 100 > > > read | write > disk fragmented I/Os ios % cum % | ios % cum % > 0: 51181 22 22 | 0 0 0 > 1: 45280 19 42 | 82206 31 31 > 2: 16615 7 49 | 29108 11 42 > 3: 3425 1 50 | 17392 6 49 > 4: 110445 48 98 | 129481 49 98 > 5: 1661 0 99 | 2702 1 99 > > read | write > disk I/O size ios % cum % | ios % cum % > 4K: 45889 8 8 | 56240 7 7 > 8K: 3658 0 8 | 6416 0 8 > 16K: 7956 1 10 | 4703 0 9 > 32K: 4527 0 11 | 11951 1 10 > 64K: 114369 20 31 | 134128 18 29 > 128K: 5095 0 32 | 17229 2 31 > 256K: 7164 1 33 | 30826 4 35 > 512K: 369512 66 100 | 465719 64 100 > > Oddly, there's no 1024K row in the I/O size table... > > > ...and these seem small to me as well, but I can't seem to change them. > Writing new values to either doesn't change anything. > > # cat /sys/block/sdb/queue/max_hw_sectors_kb > 320 > # cat /sys/block/sdb/queue/max_sectors_kb > 320 > > Hardware in question is DELL PERC 6/E and DELL PERC H800 RAID > controllers, with MD1000 and MD1200 arrays, respectively. > > > Any clues on where I should look next? > > Thanks, > > Kevin > > Kevin Hildebrand > University of Maryland, College Park > Office of Information Technology > _______________________________________________ > Lustre-discuss mailing list > [email protected] > http://lists.lustre.org/mailman/listinfo/lustre-discuss > _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
