Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
/ 2007-01-05 15:48:15 -0600 \ Weilin Gong: > Forgot to mention, DRBD version is 0.7.11. > Hi, > > I ran some drbd performance tests with 'tiobench': > > tiobench.pl --identifier drbd-connected --size 5000 --numruns 1 --dir / > secroot --block 4096 --threads 4 > > noticed the huge max latency numbers with Sequential Writes: let me help you with the formating... > Unit information > ================ > File size = megabytes > Blk Size = bytes > Rate = megabytes per second > CPU% = percentage of CPU used during the test > Latency = milliseconds > Lat% = percent of requests that took longer than X seconds > CPU Eff = Rate divided by CPU% - throughput per cpu load > > ┌─────────────────┬─────┬─────┬────┬─────┬───────┬───────┬─────────┬───────┬───────┬─────┐ > │Identifier │File │Blk │Num │Rate │Maximum│Avg │Max │Lat% > │Lat% > │CPU │ > │ │Size │Size │Thr │ │CPU% │Latency│Latency │2s │10s │Eff │ > ├─────────────────┼─────┼─────┼────┼─────┼───────┼───────┼─────────┼───────┼───────┼─────┤ > │Raw-device │5000 │4096 │4 │31.24│26.80% │0.364 │5635.06 │0.00242│0.00000│117 │ > ├─────────────────┼─────┼─────┼────┼─────┼───────┼───────┼─────────┼───────┼───────┼─────┤ > │Drbd-disconnected│5000 │4096 │4 │33.18│26.29% │0.319 │110394.58│0.00190│0.00016│126 │ > ├─────────────────┼─────┼─────┼────┼─────┼───────┼───────┼─────────┼───────┼───────┼─────┤ > │Drbd-connected │5000 │4096 │4 │20.88│50.18% │0.457 │135712.09│0.00110│0.00008│42 │ > └─────────────────┴─────┴─────┴────┴─────┴───────┴───────┴─────────┴───────┴───────┴─────┘ > > My lab setting: > ● Two Linux nodes on 2.6.10_mvlcge401-pc_target-x86_pentium3-P3SMP. > ● Dual-core Intel Xeon 2GHz CPU, 4GB Memory, 1Gbits/s network interface. > ● 5.7GB partition on SCSI disk, ext2 file system with the "-T largefile4" > option. > ● DRBD rate=100M; protocal C; sndbuf-size 1024k. > I don't believe the disk (~50MB/s) or network may be the factors here. You > can see the big number jump even with the DRBD disconnected mode. of course, drbd housekeeping adds latency. _especially_ in disconnected mode (activity-log and dirty-bitmap updates). but I also see the _average_ latency _drop_ and the rate increase for drbd-disconnected... so, how do you like me to explain that? the much higher average latency for drbd connected may be due to network latency. overall throughput is minimum, overall latency is _sum_ of the respective component values. > Any help on analyzing/identifying the problem will be greatly appreciated. > > Weilin * try again with a higher numruns, to get better statistics * try again with 0.7.22 * try again with drbd 8 (well, rcX, or svn trunk) * try again with large "al-extends" and then again in a second run... * what is the real storage device? sdX ? mdX ? lvm something? * what is the meta data storage device? -- : Lars Ellenberg Tel +43-1-8178292-0 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Vivenotgasse 48, A-1120 Vienna/Europe http://www.linbit.com : __ please use the "List-Reply" function of your email client.