If the re-build is slow, I would expect the array to have bad performance even after it has finished re-building. I think you problems are beyond me! Good luck! Guy -----Original Message----- From: PAulN [mailto:pauln@xxxxxxx] Sent: Thursday, August 19, 2004 2:24 PM To: Guy Cc: linux-raid@xxxxxxxxxxxxxxx Subject: Re: Raid5 Construction Question I have it mounted now but the performance sucks because the resync is going on. I've already test each disk individually and I get 38MB/sec. The machine is a 2,.4 GHz xeon with 2GB ram so there should be no problem with cpu or memory. Before I tried raid5 i made an 8xraid0 stripe which yielded ~120MB/sec which is what I'd expect from the controller. So there is no way to initialize the raid5 device - similar to what a hardware raid controller does? p Guy wrote: >You don't need to wait. You can use the array now. > >But ouch 305K/sec! If this a 386-33? :) > >Have you tried dd tests on each disk to verify each works well? > >Something like: >time dd if=/dev/sdc1 of=/dev/null bs=64k count=100000 >This is just a read test. My disks take about 340 seconds. Yours should be >about twice as fast. > >Each disk should give about the same performance. >You may find 1 that has issues. > >If you are willing to re-build the array, you could do a write test: >time dd if=/dev/zero of=/dev/sdc1 bs=64k count=10000 >THIS WILL TRASH THE ARRAY!!! > >Guy > >-----Original Message----- >From: linux-raid-owner@xxxxxxxxxxxxxxx >[mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of PAulN >Sent: Thursday, August 19, 2004 1:53 PM >To: Guy >Cc: linux-raid@xxxxxxxxxxxxxxx >Subject: Re: Raid5 Construction Question > >Guy, >thanks for the snappy reply! I wish my disks were as fast :) >I failed to mention that I had been tweaking those proc values. Currently >they are: >(root@lcn0:raid)# cat speed_limit_max >200000 >(root@lcn0:raid)# cat speed_limit_min >10000 > >If I'm correct, this means that the min speed is 10MB/sec per device. >I've verified that each device has a seq write speed of about 38MB/sec so >each should be capable of handling 10,000Kbytes sec. Right after I issue >a raidstart the speed is pretty good (~30MB/sec) but is just falls until >it hits >around 300K. > >md0 : active raid5 sdh1[7] sdf1[6] sdg1[5] sde1[4] sdd1[3] sdc1[2] >sdb1[1] sda1[0] > 481949184 blocks level 5, 64k chunk, algorithm 2 [7/7] [UUUUUUU] > [>....................] resync = 2.4% (1936280/80324864) >finish=4261.4min speed=305K/sec > >In the docs I saw that "reconstruction" is possible with raidhotadd but >I didn't >see anything about initialization. So am I "screwed" until the resync >is fixed? I was depeding >on the disks to do some filesystem testing but maybe I'll have to wait a >few days.. >Thanks, >Paul > > >Guy wrote: > > > >>In short... Issue this command: >>echo 100000 > /proc/sys/dev/raid/speed_limit_max >> >>If it does not help issue this command and send the results: >>cat /proc/mdstat >> >>Details below. >> >>These are related to throttling: >>/proc/sys/dev/raid/speed_limit_max >>/proc/sys/dev/raid/speed_limit_min >> >>Do "man md" for more info. >> >>The speed limits are per device, not per array. >>Make sure the max is large enough the permit your disks to go as fast as >>they can. I use 100000 (100,000K bytes/second). My disks are not that >>fast, and having too large of a number does not hurt. >>At least as a test, set the min to the same value as max. >> >>I use these commands when I want to change by hand: >>cat /proc/sys/dev/raid/speed_limit_max >>cat /proc/sys/dev/raid/speed_limit_min >> >>echo 100000 > /proc/sys/dev/raid/speed_limit_max >>echo 1000 > /proc/sys/dev/raid/speed_limit_min >> >>Guy >> >>-----Original Message----- >>From: linux-raid-owner@xxxxxxxxxxxxxxx >>[mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of PAulN >>Sent: Thursday, August 19, 2004 1:25 PM >>To: linux-raid@xxxxxxxxxxxxxxx >>Subject: Raid5 Construction Question >> >>Hi, >>So I have a raid 5 which is around ~1TB and the problem I've been having >>is that >>the resync rate is really bad. This is understandable given that the >>raid5 has not >>been initialized. Does anyone know a way for me to initialize my raid5 >>before I use it so >>that the resync process doesn't run for 3 days? >>thanks >>paul >> >> >>Config: >>------------------------------------------------- >>raiddev /dev/md0 >>raid-level 5 >>nr-raid-disks 7 >>nr-spare-disks 1 >>chunk-size 64k >>persistent-superblock 1 >>parity-algorithm left-symmetric >> device /dev/sda1 >> raid-disk 0 >> device /dev/sdb1 >> raid-disk 1 >> device /dev/sdc1 >> raid-disk 2 >> device /dev/sdd1 >> raid-disk 3 >> device /dev/sde1 >> raid-disk 4 >> device /dev/sdg1 >> raid-disk 5 >> device /dev/sdf1 >> raid-disk 6 >> device /dev/sdh1 >> spare-disk 0 >>---------------------------------------- >> >>- >>To unsubscribe from this list: send the line "unsubscribe linux-raid" in >>the body of a message to majordomo@xxxxxxxxxxxxxxx >>More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> >> > > >- >To unsubscribe from this list: send the line "unsubscribe linux-raid" in >the body of a message to majordomo@xxxxxxxxxxxxxxx >More majordomo info at http://vger.kernel.org/majordomo-info.html > > - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
