Re: Slow disks.
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Hi, [ccing linux-ide] Please provide the part of kernel log showing initialization of your disk controller(s) as well as detection of all the discs. Verbose lspci output for the disc controller and $(smartctl -i -A $disk) output might be useful as well. Did you try the individual discs on a completely different system (e.g. plain desktop system) and what revision of SATA are both components supporting? Bruno On Mon, 20 December 2010 Rogier Wolff <R.E.Wolff@xxxxxxxxxxxx> wrote: > Hi, > > A friend of mine has a server in a datacenter somewhere. His machine > is not working properly: most of his disks take 10-100 times longer > to process each IO request than normal. > > iostat -kx 10 output: > Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util > sdd 0.30 0.00 0.40 1.20 2.80 1.10 4.88 0.43 271.50 271.44 43.43 > > shows that in this 10 second period, the disk was busy for 4.3 seconds > and serviced 15-16 requests during that time. > > Normal disks show "svctm" of around 10-20ms. > > Now you might say: It's his disk that's broken. > Well no: I don't believe that all four of his disks are broken. > (I just showed you output about one disk, but there are 4 disks in there > all behaving similar, but some are worse than others.) > > Or you might say: It's his controller that's broken. So we thought > too. We replaced the onboard sata controller with a 4-port sata > card. Now they are running off the external sata card... Slightly > better, but not by much. > > Or you might say: it's hardware. But suppose the disk doesn't properly > transfer the data 9 times out of 10, wouldn't the driver tell us > SOMETHING in the syslog that things are not fine and dandy? Moreover, > In the case above, 12kb were transferred in 4.3 seconds. If CRC errors > were happening, the interface would've been able to transfer over > 400Mb during that time. So every transfer would need to be retried on > average 30000 times... Not realistic. If that were the case, we'd > surely hit a maximum retry limit every now and then? > > > These syptoms started when the system was running 2.6.33, but are > still present now the system has been upgraded to 2.6.36. > > Is there anything you can suggest to get to the root of this problem? > Could this be a software issue with the driver? Can we enable some > driver debugging to find out what is wrong? > > Any help will be appreciated. > > Roger. > -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html