Kevin Hildebrand wrote: > > The PERC 6 and H800 use megaraid_sas, I'm currently running > 00.00.04.17-RH1. > > The max_sectors numbers (320) are what is being set by default- I am > able to set it to something smaller than 320, but not larger.
Right. You can not set max_sectors_kb larger than max_hw_sectors_kb (Linux normally defaults most drivers to 512, but Lustre sets them to be the same): you may want to instrument your HBA driver to see what is going on (ie, why the max_hw_sectors_kb is < 1024). I don't know if it is due to a driver limitation or a true hardware limit. Most drivers have a limit of 512KB by default; see Bug 22850 for the patches that fixed the QLogic and Emulex fibre channel drivers. Kevin > Kevin > > On Wed, 11 May 2011, Kevin Van Maren wrote: > >> 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
