Re: Device utilization with RAID-1

["Stefan /*St0fF*/ Hübner" <st0ff@gmx.net>]

Am 18.08.2011 03:42, schrieb NeilBrown:
> On Thu, 18 Aug 2011 02:26:17 +0200 Harald Nikolisin <hochglanz@gmail.com>
> wrote:
> 
>> hi,
>>
>> I didn't want to complain in general about SW RAID-1 performance. I
>> simply think something is wrong with my setup and I have currently no
>> idea how to improve.
>>
>> The basic questions (where I did not find an answer, neither in FAQ's
>> nor in forum discussions) are.
>> a) Is it normal that the hard drives show an permanent utilization
>> (around 20%) without any noticeable actions on the computer?
> 
> No.  If the array is resyncing or recovering then you would expect
> utilization for as many hours as it takes - but that would show
> in /proc/mdstat.
> 
>> b) Should (as long as no resync happens) the state of mdadm active or clean?
> 
> If anything has been written to the device in the last 200msec (including
> e.g. access time updates) then expect it to be 'active'.
> If nothing has been written for 200msecc or more, then expect it to be clean.
> 
> If you crash while it is active, a resync is needed.
> If you crash while it is clean, no resync is needed.
> If you don't crash at all .... that is best :-)
> 
> NeilBrown
> 

I second that ;)  Have you checked the SMART-Attributes of your disks,
are they still OK?  But if they weren't, you wouldn't see that they're a
bit more busy, you'd only feel it from bad performance.

Indeed I think you need to find out which processes create your I/O
load, as it seems to be kind of a badly configured service/daemon which
slows down your whole computer that way... It's probably a good idea to
start with dstat and a wide screen :)

Stefan

> 
> 
>>
>> cheers,
>>   harald
>>
>> well, I have only 2 hard drives and no space for more..
>>
>> Am 16.08.2011 03:29, schrieb Roberto Spadim:
>>> try raid10 far layout
>>>
>>> 2011/8/15 Harald Nikolisin <hochglanz@gmail.com
>>> <mailto:hochglanz@gmail.com>>
>>>
>>>     Since a long time I'm unhappy with the performance of my RAID-1 system.
>>>     Investigation with atop and iostat unveils that the disk utilization is
>>>     always on a certain level although nothing happens on the system. In the
>>>     case of reading or writing files the utilization boosts always to 100%
>>>     for a long time. Very ugly examples are "Firefox starting" or "zypper
>>>     updates".
>>>     That is snapshot of the output of iostat:
>>>
>>>
>>>     Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
>>>     avgrq-sz avgqu-sz   await  svctm  %util
>>>     sda               0,00     0,00    0,00    7,33     0,00    43,33
>>>     5,91     0,33   43,18  33,32  24,43
>>>     sdb               0,00     0,00    0,00    7,33     0,00    43,33
>>>     5,91     0,35   45,59  39,73  29,13
>>>     md0               0,00     0,00    0,00    0,67     0,00     5,33
>>>     8,00     0,00    0,00   0,00   0,00
>>>     md1               0,00     0,00    0,00    0,33     0,00     5,33
>>>     16,00     0,00    0,00   0,00   0,00
>>>     md2               0,00     0,00    0,00    0,33     0,00     1,00
>>>     3,00     0,00    0,00   0,00   0,00
>>>     md3               0,00     0,00    0,00    0,00     0,00     0,00
>>>     0,00     0,00    0,00   0,00   0,00
>>>     md4               0,00     0,00    0,00    0,00     0,00     0,00
>>>     0,00     0,00    0,00   0,00   0,00
>>>     md5               0,00     0,00    0,00    0,33     0,00     0,67
>>>     2,00     0,00    0,00   0,00   0,00
>>>
>>>     I checked with mdadm if a resync happens or so, but this is not the
>>>     case. The state says "active" on all RAID devices - btw. what is the
>>>     difference to "clean" ?
>>>
>>>     thanks for any hints,
>>>      harald
>>>     --
>>>     To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>>     the body of a message to majordomo@vger.kernel.org
>>>     <mailto:majordomo@vger.kernel.org>
>>>     More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>>
>>>
>>>
>>> -- 
>>> Roberto Spadim
>>> Spadim Technology / SPAEmpresarial
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html