Phil Stracchino wrote: > On 04/08/10 03:53, Craig Ringer wrote: >> BTW, When I suggested that greater write concurrency would be desirable >> and should be easier, Phil Stracchino raised some concerns about >> concurrent writes to a file system increasing fragmentation and hurting >> overall performance. Rather than just wave my hands about that I've put >> together a testing tool for concurrently writing big files from multiple >> threads that optionally uses posix_fallocate to pre-allocate ahead in >> chunks up to total file size. It tracks per-thread and total runtime and >> time spent in write() and posix_fallocate() calls. I'm doing some tests >> with it now and will post it to the bacula-devel list too. I'm planning >> on testing the real effects of various levels of concurrent writes on >> common file systems with it using a controlling shell script and will >> report back when that eventually finishes. > > I'll be interested to see those results. Which filesystems are you testing?
I'm interested in ext3, ext4 and xfs. I should probably look at zfs too, but don't have any hosts that it runs on usefully and don't really have any personal interest in it. I've posted the tool's sources & makefile to the devel list along with some preliminary notes. So far it looks like posix_fallocate is, as expected, a win if you know the volume size (or a reasonable approximation of it) in advance, and not much help or a loss if you don't so you posix_fallocate(...) smaller chunks progressively. Further info will appear on -devel once I've put it together. -- Craig Ringer ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users