磨砺技术珠矶，践行数据之道，追求卓越价值
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[作者 高健@博客园 luckyjackgao@gmail.com]
可资参考的资料：
首先用 hdparm测试磁盘读取的最大带宽:
hdparm --direct -t /dev/sda
测试结果为200MB/s以上。
然后给用户postgres设置参数，保持磁盘读写I/O为10MB/秒以下（此用户名下所有进程总和）。
# Configuration file generated by cgsnapshotmount { cpuset = /cgroup/cpuset; cpu = /cgroup/cpu; cpuacct = /cgroup/cpuacct; memory = /cgroup/memory; devices = /cgroup/devices; freezer = /cgroup/freezer; net_cls = /cgroup/net_cls; blkio = /cgroup/blkio;}group io-test { perm { task{ uid=postgres; gid=postgres; } admin{ uid=root; gid=root; } } blkio { blkio.throttle.write_iops_device=""; blkio.throttle.read_iops_device=""; blkio.throttle.write_bps_device="8:0 10485760"; blkio.throttle.read_bps_device="8:0 10485760"; blkio.reset_stats=""; blkio.weight="500"; blkio.weight_device=""; }}[postgres@cent6 Desktop]$ 再看
[postgres@cent6 Desktop]$ cat /etc/cgrules.conf# /etc/cgrules.conf##Each line describes a rule for a user in the forms:### : ##Where:# can be:# - an user name# - a group name, with @group syntax# - the wildcard *, for any user or group.# - The %, which is equivalent to "ditto". This is useful for# multiline rules where different cgroups need to be specified# for various hierarchies for a single user.## is optional and it can be:# - a process name# - a full command path of a process## can be:# - comma separated controller names (no spaces)# - * (for all mounted controllers)## can be:# - path with-in the controller hierarchy (ex. pgrp1/gid1/uid1)## Note:# - It currently has rules based on uids, gids and process name.## - Don't put overlapping rules. First rule which matches the criteria# will be executed.## - Multiline rules can be specified for specifying different cgroups# for multiple hierarchies. In the example below, user "peter" has# specified 2 line rule. First line says put peter's task in test1/# dir for "cpu" controller and second line says put peter's tasks in# test2/ dir for memory controller. Make a note of "%" sign in second line.# This is an indication that it is continuation of previous rule.### ##john cpu usergroup/faculty/john/#john:cp cpu usergroup/faculty/john/cp#@student cpu,memory usergroup/student/#peter cpu test1/#% memory test2/#@root * admingroup/#* * default/postgres blkio io-test/# End of file###[postgres@cent6 Desktop]$
先用dd命令实际测试看看：
[postgres@cent6 Desktop]$ dd if=/dev/zero of=testfile2 bs=4K count=1024 oflag=direct1024+0 records in1024+0 records out4194304 bytes (4.2 MB) copied, 0.372953 s, 11.2 MB/s[postgres@cent6 Desktop]$ dd if=/dev/zero of=testfile2 bs=8K count=1024 oflag=direct1024+0 records in1024+0 records out8388608 bytes (8.4 MB) copied, 0.733823 s, 11.4 MB/s[postgres@cent6 Desktop]$ dd if=/dev/zero of=testfile2 bs=8K count=1024 oflag=direct1024+0 records in1024+0 records out8388608 bytes (8.4 MB) copied, 0.733256 s, 11.4 MB/s[postgres@cent6 Desktop]$ [postgres@cent6 Desktop]$ dd if=/dev/zero of=testfile2 bs=16K count=1024 oflag=direct1024+0 records in1024+0 records out[postgres@cent6 Desktop]$
当然，如果dd执行时，开数据块太多，又是这种完全空的块，误差就会增大：
[postgres@cent6 Desktop]$ dd if=/dev/zero of=testfile1 bs=10240 count=300000300000+0 records in300000+0 records out3072000000 bytes (3.1 GB) copied, 57.6779 s, 53.3 MB/s[postgres@cent6 Desktop]$
用实际的下载动作进行测试：
[postgres@cent6 Desktop]$ wget http://centos.arcticnetwork.ca/6.4/isos/x86_64/CentOS-6.4-x86_64-LiveCD.iso
再看看IO状态：
[postgres@cent6 Desktop]$ iostat -x 20Linux 2.6.32-279.el6.x86_64 (cent6.gao) 09/10/2013 _x86_64_ (1 CPU)avg-cpu: %user %nice %system %iowait %steal %idle 1.38 0.00 3.55 12.16 0.00 82.91Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %utilsda 7.50 1747.20 7.77 24.88 535.75 14224.09 452.17 12.54 384.25 4.41 14.40dm-0 0.00 0.00 13.79 1771.99 524.65 14224.07 8.26 1975.37 1106.16 0.09 16.73dm-1 0.00 0.00 0.38 0.00 3.03 0.00 8.00 0.00 3.68 2.34 0.09avg-cpu: %user %nice %system %iowait %steal %idle 3.65 0.00 2.14 0.73 0.00 93.48Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %utilsda 0.00 1.82 1.09 1.56 49.64 25.44 28.24 0.03 11.78 3.57 0.95dm-0 0.00 0.00 1.04 3.18 48.80 25.44 17.58 0.03 7.35 2.15 0.91dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00avg-cpu: %user %nice %system %iowait %steal %idle 1.65 0.00 1.65 0.98 0.00 95.72Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %utilsda 0.00 60.28 0.00 1.44 0.00 492.12 341.14 0.02 11.79 8.86 1.28dm-0 0.00 0.00 0.00 61.51 0.00 492.12 8.00 0.59 9.54 0.21 1.28dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
除了一开始的峰值，util长期在2%-3%之间，基本达到效果。
[作者 高健@博客园 luckyjackgao@gmail.com]
磨砺技术珠矶，践行数据之道，追求卓越价值
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