Hi, Yeah, the performance when the system isn't waiting for slow IO's is definitely acceptable for what I'm doing, it's just the handful of slow IO's messing up the overall latency.
Bill ________________________________ From: Gonzalo Aguilar Delgado [gagui...@aguilardelgado.com] Sent: Monday, January 05, 2015 3:47 PM To: Sanders, Bill Cc: ceph-users@lists.ceph.com Subject: Re: [ceph-users] Slow/Hung IOs Hi, I just ran this test and found my system is not better. But I use commodity hardware. The only difference is latency. You should look at it. Total time run: 62.412381 Total writes made: 919 Write size: 4194304 Bandwidth (MB/sec): 58.899 Stddev Bandwidth: 27.7791 Max bandwidth (MB/sec): 108 Min bandwidth (MB/sec): 0 Average Latency: 2.15587 Stddev Latency: 1.1327 Max latency: 6.42248 Min latency: 0.444754 I use 2 nodes 1GB net, but only get 100MB/s. I will look at it and increase node number. Best regards, El lun, 5 de ene 2015 a las 11:36 , Sanders, Bill <bill.sand...@teradata.com> escribió: Hi Ceph Users, We've got a Ceph cluster we've built, and we're experiencing issues with slow or hung IO's, even running 'rados bench' on the OSD cluster. Things start out great, ~600 MB/s, then rapidly drops off as the test waits for IO's. Nothing seems to be taxed... the system just seems to be waiting. Any help trying to figure out what could cause the slow IO's is appreciated. For example, 'rados -p rbd bench 60 write -t 32' takes over 900s to complete: A typical rados bench: Total time run: 957.458274 Total writes made: 9251 Write size: 4194304 Bandwidth (MB/sec): 38.648 Stddev Bandwidth: 157.323 Max bandwidth (MB/sec): 964 Min bandwidth (MB/sec): 0 Average Latency: 3.21126 Stddev Latency: 51.9546 Max latency: 910.72 Min latency: 0.04516 According to ceph.log, we're not experiencing any OSD flapping or monitor election cycles, just slow requests: # grep slow /var/log/ceph/ceph.log: 2015-01-05 13:42:42.937678 osd.18 39.7.48.7:6803/11185 220 : [WRN] 3 slow requests, 1 included below; oldest blocked for > 513.611379 secs 2015-01-05 13:42:42.937685 osd.18 39.7.48.7:6803/11185 221 : [WRN] slow request 30.136429 seconds old, received at 2015-01-05 13:42:12.801205: osd_op(client.92008.1:3101508 rb.0.1437.238e1f29.00000000000f [write 114688~512] 3.841c0edf ondisk+write e994) v4 currently waiting for subops from 3,37 2015-01-05 13:42:49.938681 osd.18 39.7.48.7:6803/11185 222 : [WRN] 3 slow requests, 1 included below; oldest blocked for > 520.612372 secs 2015-01-05 13:42:49.938688 osd.18 39.7.48.7:6803/11185 223 : [WRN] slow request 480.636547 seconds old, received at 2015-01-05 13:34:49.302080: osd_op(client.92008.1:3100010 rb.0.140d.238e1f29.000000000c77 [write 3622400~512] 3.d031a69f ondisk+write e994) v4 currently waiting for subops from 26,37 2015-01-05 13:43:12.941838 osd.18 39.7.48.7:6803/11185 224 : [WRN] 3 slow requests, 1 included below; oldest blocked for > 543.615545 secs 2015-01-05 13:43:12.941844 osd.18 39.7.48.7:6803/11185 225 : [WRN] slow request 60.140595 seconds old, received at 2015-01-05 13:42:12.801205: osd_op(client.92008.1:3101508 rb.0.1437.238e1f29.00000000000f [write 114688~512] 3.841c0edf ondisk+write e994) v4 currently waiting for subops from 3,37 2015-01-05 13:44:04.933440 osd.14 39.7.48.7:6818/11640 251 : [WRN] 4 slow requests, 1 included below; oldest blocked for > 606.941954 secs 2015-01-05 13:44:04.933469 osd.14 39.7.48.7:6818/11640 252 : [WRN] slow request 240.101138 seconds old, received at 2015-01-05 13:40:04.832272: osd_op(client.92008.1:3101102 rb.0.142b.238e1f29.000000000010 [write 475136~512] 3.5e623815 ondisk+write e994) v4 currently waiting for subops from 27,33 2015-01-05 13:44:12.950805 osd.18 39.7.48.7:6803/11185 226 : [WRN] 3 slow requests, 1 included below; oldest blocked for > 603.624511 secs 2015-01-05 13:44:12.950812 osd.18 39.7.48.7:6803/11185 227 : [WRN] slow request 120.149561 seconds old, received at 2015-01-05 13:42:12.801205: osd_op(client.92008.1:3101508 rb.0.1437.238e1f29.00000000000f [write 114688~512] 3.841c0edf ondisk+write e994) v4 currently waiting for subops from 3,37 2015-01-05 13:46:12.988010 osd.18 39.7.48.7:6803/11185 228 : [WRN] 3 slow requests, 1 included below; oldest blocked for > 723.661722 secs 2015-01-05 13:46:12.988017 osd.18 39.7.48.7:6803/11185 229 : [WRN] slow request 240.186772 seconds old, received at 2015-01-05 13:42:12.801205: osd_op(client.92008.1:3101508 rb.0.1437.238e1f29.00000000000f [write 114688~512] 3.841c0edf ondisk+write e994) v4 currently waiting for subops from 3,37 2015-01-05 13:46:18.971570 osd.14 39.7.48.7:6818/11640 253 : [WRN] 4 slow requests, 1 included below; oldest blocked for > 740.980083 secs 2015-01-05 13:46:18.971577 osd.14 39.7.48.7:6818/11640 254 : [WRN] slow request 480.063439 seconds old, received at 2015-01-05 13:38:18.908100: osd_op(client.91911.1:3113675 rb.0.13f5.238e1f29.000000000010 [write 475136~512] 3.679a939d ondisk+write e994) v4 currently waiting for subops from 27,34 2015-01-05 13:48:05.030581 osd.14 39.7.48.7:6818/11640 255 : [WRN] 4 slow requests, 1 included below; oldest blocked for > 847.039098 secs 2015-01-05 13:48:05.030587 osd.14 39.7.48.7:6818/11640 256 : [WRN] slow request 480.198282 seconds old, received at 2015-01-05 13:40:04.832272: osd_op(client.92008.1:3101102 rb.0.142b.238e1f29.000000000010 [write 475136~512] 3.5e623815 ondisk+write e994) v4 currently waiting for subops from 27,33 iostat -dxm: Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util sda 5662.99 3.63 155.17 3.37 22.94 0.03 296.72 1.05 6.64 1.79 28.32 sdb 0.73 0.04 3.62 70.66 0.04 10.85 300.04 0.06 0.79 0.08 0.61 sdc 0.70 0.00 1.70 65.45 0.01 10.34 315.60 0.06 0.85 0.09 0.57 sdd 0.07 0.95 16.78 13.47 1.03 2.28 224.25 0.37 12.32 3.84 11.62 sde 0.26 0.80 25.79 10.89 2.11 1.85 220.74 2.82 76.94 4.73 17.35 sdf 0.23 0.94 21.16 12.39 1.56 2.14 225.94 2.81 83.84 4.70 15.75 sdg 0.02 0.91 9.22 12.30 0.33 2.06 227.64 0.26 12.26 3.67 7.89 sdh 0.07 0.86 14.31 12.35 0.84 2.06 223.02 2.17 81.27 4.79 12.76 sdk 0.19 0.85 15.92 10.48 1.06 1.78 220.09 3.11 114.07 4.68 12.35 sdl 0.30 0.87 20.32 12.07 1.45 2.06 221.99 2.71 82.65 4.68 15.16 sdi 0.13 0.88 16.03 11.51 1.07 1.94 224.27 2.99 108.40 4.64 12.78 sdj 0.15 0.90 15.63 11.83 0.95 2.01 220.32 2.85 103.83 4.65 12.76 sdm 0.19 0.86 20.48 12.04 1.46 2.04 220.42 2.64 81.17 4.72 15.34 Our ceph cluster is 4x Dell R720xd nodes: 2x1TB spinners configured in RAID for the OS 10x4TB spinners for OSD's (XFS) 2x400GB SSD's, each with 5x~50GB OSD journals 2x Xeon E5-2620 CPU (/proc/cpuinfo reports 24 cores) 128GB RAM Two networks (public+cluster), both over infiniband Three monitors are configured on the first three nodes, and use a chunk of one of the SSDs for their data, on an XFS partition Software: SLES 11SP3, with some in house patching. (3.0.1 kernel, "ceph-client" backported from 3.10) Ceph version: ceph-0.80.5-0.9.2, packaged by SUSE ceph.conf: fsid = 3e8dbfd8-c3c8-4d30-80e2-cd059619d757 mon initial members = tvsaq1, tvsaq2, tvsar1 mon host = 39.7.48.6, 39.7.48.7, 39.7.48.8 cluster network = 39.64.0.0/12 public network = 39.0.0.0/12 auth cluster required = cephx auth service required = cephx auth client required = cephx osd journal size = 9000 filestore xattr use omap = true osd crush update on start = false osd pool default size = 3 osd pool default min size = 1 osd pool default pg num = 4096 osd pool default pgp num = 4096 mon clock drift allowed = .100 osd mount options xfs = rw,noatime,inode64
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