From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Peter Kirk Subject: System goes very slow (was: Re: [linux-lvm] Test of LVM) Date: Sun, 27 May 2001 04:56:24 +0200 References: <01052614354500.00527@notch> <20010526154903.A1477@dardhal.mired.net> In-Reply-To: <20010526154903.A1477@dardhal.mired.net> MIME-Version: 1.0 Message-Id: <01052704562400.02599@notch> Content-Transfer-Encoding: 8bit Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: List-Id: Content-Type: text/plain; charset="us-ascii" To: linux-lvm@sistina.com This is what bonnie gives me Am Samstag, 26. Mai 2001 17:49 schrieben Sie: > On Saturday, 26 May 2001, at 14:35:45 +0200, > > Peter Kirk wrote: > > Hi, > > > > I have two disks in one Logical Volume, and all "Partitions" in the LV > > are striped over the disks, the two disks are both: > > I suppose you mean "a VG consiting of the two disks, with LV created with > --stripe=2, that is like a RAID-0 would do" :) I have no idea of what I mean, in the setup with SuSE`s installer (yast) there was this place to set the stripe option, which I set to two. > > > Now I would like to know, how to test if my LVM is performing as it > > should, [...] > > Depending on what you want to test, you can use several methods/tools > ranging from dd'ing data in and out, recursive copying, hdparm, bonnie, > bonnie++ and mongo. Check http://bulma.lug.net/static to see some > filesystem-oriented test you could try. I tried bonnie, is this result what I should have expected ? root@notch:/home/pwk > bonnie -s 1024MB Bonnie 1.2: File './Bonnie.2815', size: 1073741824, volumes: 1 Writing with putc()... done: 3270 kB/s 35.4 %CPU Rewriting... done: 1505 kB/s 19.3 %CPU Writing intelligently... done: 4682 kB/s 11.4 %CPU [I stopped bonnie here, do you need more output ?] I don't know what this test does, but surely more than 3MB/sec of writing performance should be ?? I'm not certain if this problem I am about to describe is LVM specific, but I think that the most propable cause: When I do e.g. a run of bonnie (-> My disks have work to do), the entire System goes *extremly* slow (each key hit takes about 1sec to apear on the terminal, from the command top to the coming up of the ascii chart there is a time gap of ~20sec...) As Andreas Dilger pointed out, I can't have to disks on one Controler doing things simultanously. Might this somehow be the reason why my systems snails on disk usage ? There is something I tested in such times of slowness, and that is the output of top top [normal running system + X + KDE] 319 root 17 0 196M 196M 2352 S 0.7 39.2 6:33 X 2586 pwk 12 0 12856 12M 11092 S 0.1 2.5 0:43 kdeinit 2887 root 16 0 980 980 764 R 0.1 0.1 0:00 top 1 root 9 0 216 216 180 S 0.0 0.0 0:07 init 2 root 9 0 0 0 0 SW 0.0 0.0 0:00 keventd 3 root 9 0 0 0 0 SW 0.0 0.0 0:35 kswapd 4 root 9 0 0 0 0 SW 0.0 0.0 0:00 kreclaimd 5 root 9 0 0 0 0 SW 0.0 0.0 0:14 bdflush 6 root 9 0 0 0 0 SW 0.0 0.0 0:07 kupdated top [system with bonnie running] 2815 root 17 0 544 544 440 R 37.5 0.1 4:50 bonnie 319 root 16 0 196M 196M 2352 R 15.4 39.2 6:01 X 2599 pwk 15 0 19344 18M 12580 S 12.5 3.7 1:58 kmail 2189 pwk 10 0 11540 11M 7048 S 9.9 2.2 3:21 kmix 865 pwk 9 0 3168 3168 2272 S 1.7 0.6 0:53 artsd 896 pwk 9 0 11436 11M 10220 S 1.1 2.2 1:29 kdeinit 893 pwk 9 0 14448 14M 12344 S 0.9 2.8 1:03 kdeinit 2885 pwk 12 0 980 980 764 R 0.7 0.1 0:00 top 891 pwk 10 0 14916 14M 12904 S 0.1 2.9 0:40 kdeinit 2586 pwk 9 0 12840 12M 11076 S 0.1 2.5 0:42 kdeinit 1 root 9 0 216 216 180 S 0.0 0.0 0:07 init As you see, all processes seam to take much more CPU time when bonnie is running [noting that I am not using any of the programms activly, there are only running]. I would realy love to get rid of this problem, so please help. If you think I should try one of my HD on the second controler, could you please give me some hints of how not to destroy my linux system by doing this (where do I have to change things) > > My (little) experience with stripped LVs is that throughput is quite lower > that the achieved with kernel's software RAID-0: the latter achieved > nearly the sum of the disks's R/W KB/s, while stripped LVs performance > felt quite behind. > > But this was a _very_ simple test with a Pentium75 machine, with 16 MB RAM > and two disks, 400 MB one and 800 MB the other (tested with bonnie). So > results can be far from true under more realistic setups :). > Can anybody comment on the speed difference between softraid0 and LVM ? Thank you in advance