[CentOS] Strangely slow disk

Mon Dec 5 00:38:29 UTC 2011
Timothy Murphy <gayleard at eircom.net>

Timothy Murphy wrote:

>> Check your bios, and make sure that you did not have IDE mode enabled and
>> AHCI is selected .
> 
> Thanks for your response, and for the others received.
> 
> But I should have pointed out that the slow operation
> has only started recently, in the last week or so,
> after working normally since I acquired the disk a year or so ago.

To add to the mystery, I just checked with hdparm,
and the speed of the disk (as measured this way) seems normal,
compared with various other disks:
-----------------------------------
The "slow disk"
[tim at helen ~]$ sudo hdparm -t /dev/sdb
/dev/sdb:
 Timing buffered disk reads:  168 MB in  3.00 seconds =  55.98 MB/sec
-----------------------------------
Another disk on the same machine
[tim at blanche ~]$ sudo hdparm -t /dev/sda
/dev/sda:
 Timing buffered disk reads: 146 MB in  3.01 seconds =  48.57 MB/sec
-----------------------------------
An external hard disk attached to the same machine
[tim at helen ~]$ sudo hdparm -t /dev/sdc

/dev/sdc:
 Timing buffered disk reads:   54 MB in  3.03 seconds =  17.80 MB/sec
-----------------------------------

I have Windows XP on another partition.
I don't think I've ever used it
(I always install Windows if it is not already on the machine,
as I've had a couple of occasions when it has saved my life).
I'll see how fast (or slow) Windows backup goes.

-- 
Timothy Murphy  
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College Dublin