Re: Abysmal disk performance, how to debug?

From: Stephen Clark
Date: Sat Jan 20 2007 - 22:42:02 EST


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@xxxxxx> 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


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