IBM blade server abysmal disk write performances
Wojciech Puchar
wojtek at wojtek.tensor.gdynia.pl
Tue Jan 15 21:54:24 UTC 2013
>
> # dd if=/dev/zero of=foo count=1 bs=10240000
> 1+0 records in
> 1+0 records out
> 10240000 bytes transferred in 19.579077 secs (523007 bytes/sec)
>
you write to file not device, so it will be clustered anyway by FreeBSD.
128kB by default, more if you put options MAXPHYS=... in kernel config and
recompile.
Even with hard drive write cache disabled, it should about one write
per revolution but seems to do 4 writes per second.
so probably it is not that but much worse failure.
Did you rest read speed?
dd if=/dev/disk of=/dev/null bs=512
dd if=/dev/disk of=/dev/null bs=4k
dd if=/dev/disk of=/dev/null bs=128k
?
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