On Thu, 19 Aug 2004, Guy wrote: > You don't need to wait. You can use the array now. Indeed - but maybe you are already using the array which is why the rebuild it taking so long? > 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. You can also use hdparm - although really designed for IDE drives, it'll do the test on SCSI withou any problems: Eg. on a reasonable PC with an IDE drive: /dev/hda: Timing buffer-cache reads: 1008 MB in 2.00 seconds = 504.00 MB/sec Timing buffered disk reads: 142 MB in 3.02 seconds = 47.02 MB/sec On a SCSI server (Dell 4xxxx something) /dev/sda: Timing buffer-cache reads: 128 MB in 0.18 seconds =711.11 MB/sec Timing buffered disk reads: 64 MB in 0.97 seconds = 65.98 MB/sec This is a RAID1 on the same server /dev/md0: Timing buffer-cache reads: 128 MB in 0.18 seconds =711.11 MB/sec Timing buffered disk reads: 64 MB in 1.03 seconds = 62.14 MB/sec This isa RAID5 on the same server. /dev/md4: Timing buffer-cache reads: 128 MB in 0.18 seconds =711.11 MB/sec Timing buffered disk reads: 64 MB in 0.34 seconds =188.24 MB/sec > Each disk should give about the same performance. > You may find 1 that has issues. I've seen this with IDE drives - one drive was very much slower than the other. No idea why. How is it configured? Are all 8 drives on the same cable? You might want to split them and put 4 on a cable with 2 controllers - There may still issues with PCI bus bandwidth then, but it might help things along. On that server above, I have 4 SCSI drives, 2 on each bus. sda & b on one bus, sdc and d on the 2nd. I haven't made tests to see if alternating the drives in the /etc/raditab makes a difference, but thats what I do anyway as it "feels" the right thing to do. Eg: raiddev /dev/md2 raid-level 5 nr-raid-disks 4 nr-spare-disks 0 persistent-superblock 1 chunk-size 32 device /dev/sda3 raid-disk 0 device /dev/sdc3 raid-disk 1 device /dev/sdb3 raid-disk 2 device /dev/sdd3 raid-disk 3 Reading the follow-ups, performance will be slow with the raid-speed-min parameter set high... If you want performance, during a rebuild, then set this low. Gordon - 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
