This kind of info is surprisingly hard to obtain. The gluster docs do contain some of it, ie: <http://community.gluster.org/a/linux-kernel-tuning-for-glusterfs/> I also found well-described kernel tuning parameters in the FHGFS wiki (as another distibuted fs, they share some characteristics) http://www.fhgfs.com/wiki/wikka.php?wakka=StorageServerTuning and more XFS tuning filesystem params here: <http://www.mythtv.org/wiki/Optimizing_Performance#Further_Information> and here: <http://www.mysqlperformanceblog.com/2011/12/16/setting-up-xfs-the-simple- edition> But of course, YMMV and a number of these parameters conflict and/or have serious tradeoffs, as you discovered. LSI recently loaned me a Nytro SAS controller (on-card SSD-cached) which seems pretty phenomenal on a single brick (and is predicted to perform well based on their profiling), but am waiting for another node to arrive before I can test it under true gluster conditions. Anyone else tried this hardware? hjm On Tuesday, March 05, 2013 12:34:41 PM Nikita A Kardashin wrote: > Hello all! > > This problem is solved by me today. > Root of all in the incompatibility of gluster cache and kvm cache. > > Bug reproduces if KVM virtual machine created with cache=writethrough > (default for OpenStack) option and hosted on GlusterFS volume. If any other > (cache=writeback or cache=none with direct-io) cacher used, performance of > writing to existing file inside VM is equal to bare storage (from host > machine) write performance. > > I think, it must be documented in Gluster and maybe filled a bug. > > Other question. Where I can read something about gluster tuning (optimal > cache size, write-behind, flush-behind use cases and other)? I found only > options list, without any how-to or tested cases. > > > 2013/3/5 Toby Corkindale <toby.corkindale at strategicdata.com.au> > > > On 01/03/13 21:12, Brian Candler wrote: > >> On Fri, Mar 01, 2013 at 03:30:07PM +0600, Nikita A Kardashin wrote: > >>> If I try to execute above command inside virtual machine (KVM), > >>> first > >>> time all going right - about 900MB/s (cache effect, I think), but if > >>> > >>> I > >>> > >>> run this test again on existing file - task (dd) hungs up and can be > >>> stopped only by Ctrl+C. > >>> Overall virtual system latency is poor too. For example, apt-get > >>> upgrade upgrading system very, very slow, freezing on "Unpacking > >>> replacement" and other io-related steps. > >>> Does glusterfs have any tuning options, that can help me? > >> > >> If you are finding that processes hang or freeze indefinitely, this is > >> not > >> a question of "tuning", this is simply "broken". > >> > >> Anyway, you're asking the wrong person - I'm currently in the process of > >> stripping out glusterfs, although I remain interested in the project. > >> > >> I did find that KVM performed very poorly, but KVM was not my main > >> application and that's not why I'm abandoning it. I'm stripping out > >> glusterfs primarily because it's not supportable in my environment, > >> because > >> there is no documentation on how to analyse and recover from failure > >> scenarios which can and do happen. This point in more detail: > >> http://www.gluster.org/**pipermail/gluster-users/2013-** > >> January/035118.html<http://www.gluster.org/pipermail/gluster-users/2013-J > >> anuary/035118.html> > >> > >> The other downside of gluster was its lack of flexibility, in particular > >> the > >> fact that there is no usage scaling factor on bricks, so that even with a > >> simple distributed setup all your bricks have to be the same size. Also, > >> the object store feature which I wanted to use, has clearly had hardly > >> any > >> testing (even the RPM packages don't install properly). > >> > >> I *really* wanted to deploy gluster, because in principle I like the idea > >> of > >> a virtual distribution/replication system which sits on top of existing > >> local filesystems. But for storage, I need something where operational > >> supportability is at the top of the pile. > > > > I have to agree; GlusterFS has been in use here in production for a while, > > and while it mostly works, it's been fragile and documentation has been > > disappointing. Despite 3.3 being in beta for a year, it still seems to > > have > > been poorly tested. For eg, I can't believe almost no-one else noticed > > that > > the log files were busted.. nor that the bug report has been around for > > quarter of a year without being responded to or fixed. > > > > I have to ask -- what are you moving to now, Brian? > > > > -Toby > > > > > > ______________________________**_________________ > > Gluster-users mailing list > > Gluster-users at gluster.org > > http://supercolony.gluster.**org/mailman/listinfo/gluster-**users<http://s > > upercolony.gluster.org/mailman/listinfo/gluster-users> --- Harry Mangalam - Research Computing, OIT, Rm 225 MSTB, UC Irvine [m/c 2225] / 92697 Google Voice Multiplexer: (949) 478-4487 415 South Circle View Dr, Irvine, CA, 92697 [shipping] MSTB Lat/Long: (33.642025,-117.844414) (paste into Google Maps) --- "Something must be done. [X] is something. Therefore, we must do it." Bruce Schneier, on American response to just about anything.
