On Thu, Jun 9, 2011 at 12:38 PM, Benjamin Franz <jfranz at freerun.com> wrote: > On 06/09/2011 02:24 AM, Emmanuel Noobadmin wrote: >> I'm trying to resolve an I/O problem on a CentOS 5.6 server. The >> process basically scans through Maildirs, checking for space usage and >> quota. Because there are hundred odd user folders and several 10s of >> thousands of small files, this sends the I/O wait % way high. The >> server hits a very high load level and stops responding to other >> requests until the crawl is done. >> >> I am wondering if I add another disk and symlink the sub-directories >> to that, would that free up the server to respond to other requests >> despite the wait on that disk? >> >> Alternatively, if I mdraid mirror the existing disk, would md be smart >> enough to read using the other disk while the first's tied up with the >> first process? > You should look at running your process using 'ionice -c3 program'. That > way it won't starve everything else for I/O cycles. Also, you may want > to experiment with using the 'deadline' elevator instead of the default > 'cfq' (see http://www.redhat.com/magazine/008jun05/features/schedulers/ > and http://www.wlug.org.nz/LinuxIoScheduler). Neither of those would > require you to change your hardware out. Also, setting 'noatime' for the > mount options for partition holding the files will reduce the number of > required I/Os quite a lot. > > But yes, in general, distributing your load across more disks should > improve your I/O profile. > > -- > Benjamin Franz > _______________________________________________ > Can one mount the root filesystem with noatime? -- Kind Regards Rudi Ahlers SoftDux Website: http://www.SoftDux.com Technical Blog: http://Blog.SoftDux.com Office: 087 805 9573 Cell: 082 554 7532