[Lustre-discuss] slow direct_io , slow journal .. in OST log

Mon Jan 25 08:40:21 PST 2010

Sorry Erik if i'm rising such a "bad" question, could u tell me more about
OST journal device ? I even don't know what it is as well as haven't seen it
before, in the lustre manual.

Best regards

On Mon, Jan 25, 2010 at 10:52 PM, Erik Froese <erik.froese at gmail.com> wrote:

> Is each OST journals on its own physical disk? I've seen those messages
> when there isn't enough hardware dedicated to the journal device.
> Erik
>
> On Sun, Jan 24, 2010 at 11:43 PM, Aaron Knister <aaron.knister at gmail.com>wrote:
>
>> 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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>>> Lustre-discuss at lists.lustre.org
>>> http://lists.lustre.org/mailman/listinfo/lustre-discuss
>>>
>>>
>>>
>>
>>
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