Re: Abysmal disk performance, how to debug?

[Ismail DÃnmez]

20 Oca 2007 Cts 22:10 tarihinde, Tim Schmielau ÅunlarÄ yazmÄÅtÄ: 
[...]
>
> Note that these dd "benchmarks" are completely bogus, because the data=20
> doesn't actually get written to disk in that time. For some enlightening=20
> data, try
>
>   time dd if=3D/dev/zero of=3D/tmp/1GB bs=3D1M count=3D1024; time sync
>
> The dd returns as soon as all data could be buffered in RAM. Only sync=20
> will show how long it takes to actually write out the data to disk.
> also explains why you see better results is writeout starts earlier.

Still not that bad:

[~]> 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, 53,3194 s, 20,1 MB/s

real    0m53.517s
user    0m0.003s
sys     0m3.193s

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