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Is anyone else having major I/O peaks due to logrotate or other jobs running simultaneously across multiple guests. I have one KVM server running Centos 5.4 with local disk that is seriously suffering as most of the guests rotate their syslog at the same time. Looking at the KVM server I'm seeing 11:00:01 PM CPU %user %nice %system %iowait %steal %idle 03:40:01 AM all 0.07 0.00 2.74 0.93 0.00 96.26 03:50:01 AM all 0.07 0.00 1.17 1.18 0.00 97.58 04:00:01 AM all 0.08 0.00 1.51 0.82 0.00 97.59 04:10:02 AM all 0.53 0.03 15.31 51.61 0.00 32.53 04:20:01 AM all 0.28 0.12 4.12 22.21 0.00 73.27 04:30:01 AM all 0.07 0.00 0.80 1.21 0.00 97.92 04:40:01 AM all 0.07 0.00 2.60 1.81 0.00 95.52 04:50:01 AM all 0.08 0.00 0.79 1.44 0.00 97.69 On one of the guests running Centos 4.6 the impact is so bad I get DMA timeout errors in the syslog, and occasional kernel panics. Mar 11 04:05:04 localhost kernel: hda: dma_timer_expiry: dma status == 0x21 Mar 11 04:05:14 localhost kernel: hda: DMA timeout error Mar 11 04:05:14 localhost kernel: hda: dma timeout error: status=0x50 { DriveReady SeekComplete } Mar 11 04:05:14 localhost kernel: Mar 11 04:05:14 localhost kernel: ide: failed opcode was: unknown Mar 11 04:05:59 localhost kernel: hda: dma_timer_expiry: dma status == 0x21 Mar 11 04:06:14 localhost kernel: hda: DMA timeout error Mar 11 04:06:14 localhost kernel: hda: dma timeout error: status=0x50 { DriveReady SeekComplete } One reference I've found is at * http://lonesysadmin.net/linux-virtual-machine-tuning-guide/ This suggests avoiding running scheduled jobs simultaneously across guests, and suggests using a random sleep. Does anyone else have suggestions on reducing the impact of cron/logrotate. --
Steven Ellis - Director of Worldwide Engineering, Bulletin.Net Inc - http://www.bulletin.net/ |
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