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Here is my output:

sda is an m4 Crucial SSD
sdb is a 7200rpm hard disk

Should I not be expecting fast performance from the SSD? Is is using TRIM and noatime. Both drives are formatted as ext4.

[Tue Jun 26 00:40:39 root@greg ] $ hdparm -Tt /dev/sda

 Timing cached reads:   8192 MB in  2.00 seconds = 4096.77 MB/sec
 Timing buffered disk reads: 794 MB in  3.00 seconds = 264.64 MB/sec

[Tue Jun 26 00:40:57 root@greg ] $ hdparm -Tt /dev/sdb

 Timing cached reads:   8044 MB in  2.00 seconds = 4023.43 MB/sec
 Timing buffered disk reads: 326 MB in  3.00 seconds = 108.58 MB/sec
[Tue Jun 26 00:41:12 root@greg ] $ 
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up vote 2 down vote accepted

It is not possible to answer your question without knowing more about the hardware of the computer where hdparm was run.

But my first "guess" would be that your computer only supports SATA II. The max (theoretical) throughput for SATA II is 300 MB/sec (~= 286 MiB/sec). Your result from hdparm of 264.64 MB/sec would appear to be good match to the "limitations" of SATA II .

One possible way to check my "guess" above would be to use the commands below.

sudo hdparm -I /dev/sda | grep speed
sudo hdparm -I /dev/sdb | grep speed
  • Note: I think I have specified the correct grep string in the commands above. However, if it does not work, try leaving off the grep and see what you get.)

The output I expect you will get (from the grep) should look like the line below.

*   Gen2 signaling speed (3.0Gb/s)

The above indicates the controller the drive is attached to is SATA II since
3.0 Gbits/sec is 300 MBytes/sec (3000/10 bits per byte) ~= 286 MiB/sec.
(See also this section of the Wikipedia SATA article.)

The results from running sudo lshw -class storage may also be of interest to you.

share|improve this answer
Wow. Great answer! – Gregorio Di Stefano Jun 26 '12 at 22:21

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