Re: Update on disk IO slowdown using udev

[Harald Hoyer <harald@redhat.com>]

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Ake wrote:
> To prove my point.
> 
> reboot
> 
> dd if=/rawdev/sdb of=/dev/null bs=8192k count=20
> 20+0 records in
> 20+0 records out
> 167772160 bytes transferred in 1.572609 seconds (106683964 bytes/sec)
> 
> mount -t tmpfs tmpfs /tmpfsdev
> mknod /tmpfsdev/sdb b 8 16
> dd if=/tmpfsdev/sdb of=/dev/null bs=8192k count=20
> 20+0 records in
> 20+0 records out
> 167772160 bytes transferred in 10.733471 seconds (15630746 bytes/sec)
> 
> 
> There is no filesystem on this device so bonnie is no good.
> 
> ido-i [/]# hdparm -Tt /rawdev/sdb 
> 
> /rawdev/sdb:
>  Timing buffer-cache reads:   2276 MB in  2.00 seconds = 1137.60 MB/sec
>  Timing buffered disk reads:  292 MB in  3.01 seconds =  97.15 MB/sec
> 
> ido-i [/]# hdparm -Tt /tmpfsdev/sdb 
> 
> /tmpfsdev/sdb:
>  Timing buffer-cache reads:   2276 MB in  2.00 seconds = 1137.04 MB/sec
>  Timing buffered disk reads:   42 MB in  3.01 seconds =  13.94 MB/sec
> 
> 



Ok... you got a point! very odd!

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