Re: Abysmal disk performance, how to debug?

[Gene Heskett <gene.heskett@verizon.net>]

On Saturday 20 January 2007 22:41, Stephen Clark wrote:
>Willy Tarreau wrote:
>>On Sat, Jan 20, 2007 at 02:56:20PM -0500, Stephen Clark wrote:
>>>Sunil Naidu wrote:
>>>>On 1/20/07, Willy Tarreau <w@1wt.eu> wrote:
>>>>>It is not expected to increase write performance, but it should help
>>>>>you do something else during that time, or also give more
>>>>> responsiveness to Ctrl-C. It is possible that you have fast and
>>>>> slow RAM, or that your video card uses shared memory which slows
>>>>> down some parts of memory which are not used anymore with those
>>>>> parameters.
>>>>
>>>>I did test some SATA drives, am getting these value for 2.6.20-rc5:-
>>>>
>>>>[sukhoi@Typhoon ~]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024
>>>>1024+0 records in
>>>>1024+0 records out
>>>>1073741824 bytes (1.1 GB) copied, 21.0962 seconds, 50.9 MB/s
>>>>
>>>>What can you suggest here w.r.t my RAM & disk?
>>>>
>>>>>Willy
>>>>
>>>>Thanks,
>>>>
>>>>~Akula2
>>>>-
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>>>
>>>Hi,
>>>whitebook vbi s96f core 2 duo t5600 2gb hitachi ATA     
>>> HTS721060G9AT00 using libata
>>>time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024
>>>1024+0 records in
>>>1024+0 records out
>>>1073741824 bytes (1.1 GB) copied, 10.0092 seconds, 107 MB/s
>>>
>>>real    0m10.196s
>>>user    0m0.004s
>>>sys     0m3.440s
>>
>>You have too much RAM, it's possible that writes did not complete
>> before the end of your measurement. Try this instead :
>>
>>$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 | sync
>>
>>Willy
>
>Yeah that make a difference:
> time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 | sync
>1024+0 records in
>1024+0 records out
>1073741824 bytes (1.1 GB) copied, 8.86719 seconds, 121 MB/s
>
>real    0m43.601s
>user    0m0.004s
>sys     0m3.912s

I'd reconsider my new years resolutions for figures like that:

#> time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 | sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 24.1455 seconds, 44.5 MB/s

real    0m25.218s
user    0m0.009s
sys     0m5.763s

but then I also have only a gig of ram.  So does this look normal?

-- 
Cheers, Gene
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