[Lustre-discuss] slow direct_io , slow journal .. in OST log
Aaron Knister
aaron.knister at gmail.com
Sun Jan 24 20:43:14 PST 2010
I don't necessarily think there's anything wrong with using drbd or running it over gigabit ethernet. If you stop all I/O to the lustre filesystem, what does an hdparm -t show on the sdc and drbd devices? Do you have any performance numbers for the drbd or underlying raid devices?
On Jan 24, 2010, at 11:17 PM, Lex wrote:
> Thank you for your fast reply, Aaron
>
> I'm using Giga Ethernet to synchronize data between to our fail-over node. Is there something wrong ? Tell me, please
>
> On Mon, Jan 25, 2010 at 10:35 AM, Aaron Knister <aaron.knister at gmail.com> wrote:
> My best guess (and please correct me if I'm wrong) is that those messages are because the underlying block devices are slow to respond to i/o requests. It looks like you're using DRBD. What's your interconnect?
>
> On Jan 24, 2010, at 9:42 PM, Lex wrote:
>
>> Hi list
>>
>> I have one OSS with hadware info like this :
>>
>> CPU Intel(R) xeon E5420 2.5 Ghz
>> Chipset intel 5000P
>> 8GB RAM
>>
>> With this OSS, we using 2 RAID-5 arrays as OSTs ( each has 4 x 1.5 TB hard drive with RAID controller adaptec 5805 )
>>
>> I worked quite smooth before, but, about 2 weeks ago, in /var/log/messages, i saw many warning ( i thought so) like this:
>>
>> Jan 25 08:41:23 OST6 kernel: Lustre: 9587:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 35s
>> Jan 25 08:41:34 OST6 kernel: Lustre: 9608:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 41s
>> Jan 25 08:41:34 OST6 kernel: Lustre: 9608:0:(filter_io_26.c:706:filter_commitrw_write()) Skipped 2 previous similar messages
>> Jan 25 08:41:35 OST6 kernel: Lustre: 9645:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 43s
>> Jan 25 08:58:10 OST6 kernel: Lustre: 9646:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 31s
>> Jan 25 08:59:39 OST6 kernel: Lustre: 9609:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 30s
>> Jan 25 09:01:05 OST6 kernel: Lustre: 9587:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 33s
>> Jan 25 09:03:23 OST6 kernel: Lustre: 9633:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 32s
>> Jan 25 09:11:25 OST6 kernel: Lustre: 9585:0:(filter_io_26.c:706:filter_commitrw_write()) lustre-OST0006: slow direct_io 36s
>>
>> I googled around and found that it's because a problem with oss_num_threads and even though brought it down to 64 ( followed by the function i found in the 1.8 manual: thread_number = RAM * CPU core / 128 MB, its value is 256 )
>>
>> options ost oss_num_threads=64
>>
>> It still didn't help.
>>
>> I thought it was only the harmless warning but maybe wrong, our performance is goes down quite heavily ( it's maybe because of other reason, but for now, i am only doubting slow direct_io problem )
>>
>> iostat -m 1 1
>> Linux 2.6.18-92.1.17.el5_lustre.1.8.0custom (OST6) 01/25/2010
>>
>> avg-cpu: %user %nice %system %iowait %steal %idle
>> 0.01 0.02 2.86 25.01 0.00 72.10
>>
>> Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
>> sda 1.30 0.01 0.00 11386 3469
>> sdb 1.30 0.01 0.00 11531 3469
>> sdc 131.50 12.40 0.26 11793218 249934
>> sdd 178.46 18.00 0.26 17124065 250334
>> md2 3.33 0.02 0.00 22915 2634
>> md1 0.00 0.00 0.00 0 0
>> md0 0.00 0.00 0.00 0 0
>> drbd3 480.10 12.39 0.26 11789047 249639
>> drbd6 565.85 14.89 0.26 14168452 249211
>>
>>
>> So, could anyone please tell me whether it's warning impact our system performance or not ? and if it does, give me solution or advice to resolve it, please
>>
>> Best regards
>>
>>
>>
>>
>>
>>
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>
>
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