Karl Larsen wrote:
Dave Stevens wrote:
On Friday 28 September 2007 03:00:11 pm Karl Larsen wrote:
Dave Stevens wrote:
On Friday 28 September 2007 10:50:32 am Karl Larsen wrote:
I was lead to mis-understand the data rate of my new SATA hard
drive. It indicated that the data rate was 3 GB/sec. But
you have to tell it what drive to check, so #hdparm -iItT /dev/sda for
example, if your SATA drive is the first one.
Dave
Yes but I am amazed by the results when hdparm is used right. Here is
what I got 5 minutes ago:
[root@k5di /]# hdparm -t /dev/sda
/dev/sda:
Timing buffered disk reads: 164 MB in 3.03 seconds = 54.21 MB/sec
[root@k5di /]# hdparm -t /dev/sdf
/dev/sdf:
Timing buffered disk reads: 190 MB in 3.02 seconds = 62.96 MB/sec
[root@k5di /]# hdparm -T /dev/sdf
/dev/sdf:
Timing cached reads: 1004 MB in 2.00 seconds = 501.56 MB/sec
[root@k5di /]# hdparm -T /dev/sda
/dev/sda:
Timing cached reads: 992 MB in 2.00 seconds = 496.23 MB/sec
[root@k5di /]#
So it appears that a SATA is just a tiny bit faster than a new IDE.
"Timing buffered disk reads:" is the interesting number.
"Timing cached reads:" doesn't measure the disk speed, it measures how
fast your system can transfer data from the kernel buffers to the user
buffers (memory to memory copy).
Regards,
John
