On Tue, Apr 6, 2010 at 8:28 AM, Olaf Zevenboom <olaf@xxxxxxxxxxx> wrote: > Dear List, > > We have a setup with two SATA2 1.5 TB harddisks in MD/LVM2 RAID1 setup on > Debian Lenny stock kernel. > As it is suffering from performance troubles I did take a closer look and > noticed that /dev/sda is way more intensively used than /dev/sdb. I > monitored the drives with various tools including atop. > /dev/sda is always a bit busier than /dev/sdb. This behavior can also be > seen on other systems with a similar setup (Etch and Lenny), but on this > particular system /dev/sda is about 10% more intensively used. Although I > think that is quite a lot and not as it should be I can live with that. What > worries me more is that /dev/sda can peek upto 100% disk-utilization causing > the system to be temporary unresponsive whilest /dev/sdb does not seem to > peek over 20% or so. > Any pointers on what is happening here and/or how I can resolve this issue > are quite welcome. > > Thanking you in advance, > Olaf Zevenboom > > Details: > > Running Debian Lenny with stock kernel 2.6.26-2-amd64 #1 SMP > LVM2 on top of MD > > 2 SATA2 1.5tb disks: lsscsi > [0:0:0:0] disk ATA WDC WD15EARS-00Z 80.0 /dev/sda > [1:0:0:0] disk ATA ST31500541AS CC32 /dev/sdb > > cat /proc/mdstat > Personalities : [raid1] > md1 : active raid1 sda2[0] sdb2[1] > 1464886912 blocks [2/2] [UU] > md0 : active raid1 sda1[0] sdb1[1] > 248896 blocks [2/2] [UU] > unused devices: <none> > > hdparm -tT /dev/sda > > /dev/sda: > Timing cached reads: 2890 MB in 2.00 seconds = 1445.36 MB/sec > Timing buffered disk reads: 300 MB in 3.01 seconds = 99.67 MB/sec > > hdparm -tT /dev/sdb > > /dev/sdb: > Timing cached reads: 7482 MB in 2.00 seconds = 3743.83 MB/sec > Timing buffered disk reads: 302 MB in 3.02 seconds = 100.00 MB/sec > > > -- > 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 > I suspect it's not 'sda' as much as it is the WD15EARS itself that's making sda. I purchased 6 WD10EARS drives and they simply didn't work for RAID, but even in single drive situations I see stuff going on with them I don't understand. One clue is that smartctl tells me the LOAD_CYCLE_COUNT is increasing at a rate of 30/hour and I haven't found out why. At that rate the drive is out of spec in 18 months, not 3 years, and I've seen this on two different machines. I saw problems in dmesg and /var/log/messages about reads and writes being blocked and once in awhile a kernel warning with trace back about a drive timing out. On the other hand I replaced the 1TB WD10EARS with a Raid Edition 500GB WD drive - WD5002ABYS - and I see none of these problems. My RAID1 setup is working great. I have no error or warning messages anywhere that I can find. Granted, half the storage for $10 more per drive, but it WORKS! Just my observations so far. - Mark -- 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
