RE: [Xen-users] Very slow drives, I/O - DMA issues?

["Steffen Heil" <lists@xxxxxxxxxxxxxxx>]

Hello.

I saw your post:
> /dev/hda:
>  Timing cached reads:   1380 MB in  2.00 seconds = 689.47 MB/sec
>  Timing buffered disk reads:  142 MB in  3.02 seconds =  47.02 MB/sec
> 
> /dev/hdb:
>  Timing cached reads:   1452 MB in  2.00 seconds = 725.20 MB/sec
>  Timing buffered disk reads:  138 MB in  3.02 seconds =  45.68 MB/sec

I wondered about hdparm -tT, which I didn't know.
So I tries it myself:

>hdparm -tT /dev/hd?

/dev/hda:
 Timing cached reads:   266 MB in  2.00 seconds = 132.84 MB/sec
 Timing buffered disk reads:  144 MB in  3.01 seconds =  47.82 MB/sec

/dev/hdb:
 Timing cached reads:   490 MB in  2.00 seconds = 244.92 MB/sec
 Timing buffered disk reads:  164 MB in  3.01 seconds =  54.48 MB/sec

/dev/hdc:
 Timing cached reads:   506 MB in  2.00 seconds = 252.41 MB/sec
 Timing buffered disk reads:   50 MB in  3.02 seconds =  16.54 MB/sec

/dev/hdd:
 Timing cached reads:   494 MB in  2.01 seconds = 246.32 MB/sec
 Timing buffered disk reads:   74 MB in  3.00 seconds =  24.64 MB/sec

Looks to me, my hda and hdb are way slower für cached reads only, while hdc
and hdd are way slower on both tests.

Can someone please explain me, what these tests mean and what I could
possibly do.

Regards,
  Steffen

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