Yes, difficulty finding free disk space can also be a problem, but I could not recall big changes in how that worked since 1.6, other than memory pressure from the read cache pushing out the bitmaps. See http://jira.whamcloud.com/browse/LU-15
Kevin James Rose wrote: > Hi Kevin, > > Thanks for the suggestion. I will try this out. > > For the moment it seems that it may be disk space related. I have > removed some data from the file system. Performance returned to where I > would expect it to be as space freed up (currently at 83% full). Since > free space I have seen two messages on an OSS where the number of > threads is tuned to the amount of RAM in the host and six on an OSS that > has the number of threads set higher than it should. This is a much > better situation than the steady stream I was experiencing last night. > Maybe disabling the read cache will remove the last few. > > I am still very curious what the rapid small reads seen when writing are > as this showed up while mounted ldiskfs so not doing regular lustre > operations at all. > > Thanks again for your help, > > James. > > > On Wed, 2011-04-20 at 08:48 -0300, Kevin Van Maren wrote: > >> First guess is the increased memory pressure caused by the Lustre 1.8 >> read cache. Many times "slow" messages are caused by memory >> allocatons taking a long time. >> >> You could try disabling the read cache and see if that clears up the >> slow messages. >> >> Kevin >> >> >> On Apr 20, 2011, at 4:29 AM, James Rose <james.r...@framestore.com> >> wrote: >> >> >>> Hi >>> >>> We have been experiencing degraded performance for a few days on a >>> fresh install of lustre 1.8.5 (on RHEL5 using sun ext4 rpms). The >>> initial bulk load of the data will be fine but once in use for a >>> while writes become very slow to individual ost. This will block io >>> for a few minutes and then carry on as normal. The slow writes will >>> then move to another ost. This can be seen in iostat and many slow >>> IO messages will be seen in the logs (example included) >>> >>> The osts are between 87 90 % full. Not ideal but has not caused any >>> issues running 1.6.7.2 on the same hardware. >>> >>> The osts are RAID6 on external raid chassis (Infortrend). Each ost >>> is 5.4T (small). The server is Dual AMD (4 cores). 16G Ram. Qlogic >>> FC HBA. >>> >>> I mounted the osts as ldiskfs and tried a few write tests. These >>> also show the same behaviour. >>> >>> While the write operation is blocked there will be hundreds of read >>> tps and a very small kb/s read from the raid but now writes. As >>> soon as this completes writes will go through at a more expected >>> speed. >>> >>> Any idea what is going on? >>> >>> Many thanks >>> >>> James. >>> >>> Example error messages: >>> >>> Apr 20 04:53:04 oss5r-mgmt kernel: LustreError: dumping log to /tmp/ >>> lustre-log.1303271584.3935 >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow quota >>> init 286s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow journal >>> start 39s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 39 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow >>> brw_start 39s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 38 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow journal >>> start 133s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 44 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow >>> brw_start 133s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 44 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow journal >>> start 236s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow i_mutex >>> 40s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 2 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 6 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow i_mutex >>> 277s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow >>> direct_io 286s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 3 previous >>> similar messages >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow journal >>> start 285s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 1 previous >>> similar message >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow >>> commitrw commit 285s due to heavy IO load >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: Skipped 1 previous >>> similar message >>> Apr 20 04:53:40 oss5r-mgmt kernel: Lustre: rho-OST0012: slow parent >>> lock 236s due to heavy IO load >>> >>> >>> _______________________________________________ >>> Lustre-discuss mailing list >>> Lustre-discuss@lists.lustre.org >>> http://lists.lustre.org/mailman/listinfo/lustre-discuss >>> >> _______________________________________________ >> Lustre-discuss mailing list >> Lustre-discuss@lists.lustre.org >> http://lists.lustre.org/mailman/listinfo/lustre-discuss >> > > > _______________________________________________ Lustre-discuss mailing list Lustre-discuss@lists.lustre.org http://lists.lustre.org/mailman/listinfo/lustre-discuss