HD: Large io response time from idle - cause?

[sullivang]

Using the IOMeter utility, I am noticing that the io response time of hard disks is very large (hundreds of milliseconds), if the drive is idle. I.e - the very first io to the drive is very slow, and from that point on it is fine.

If I configure IOMeter to do very sparse, single io's, then it appears that EVERY io is slow.

E.g: internal Samsung HM251JJ connected to Intel ICH9M-E RAID controller: if it is not accessed for approximately 5 seconds, the response time is about 360ms. If it is accessed more frequently than that, the access time is significantly lower. (much closer to specification)

Another example: an externally attached USB 2.0 drive (HP SimpleSave 1TB), the idle timeout is about 8 seconds, with similarly large response times if accessed at this interval or greater.

Samsung say the seek from idle of their drive is only 5.6ms, and they have recommended I contact the manufacturer of the computer.

The computer is a Dell E6500 laptop running XP SP3, processor locked on maximum frequency and drive power down disabled.
I am using NTFS for the io testing - NOT raw partitions.
io operation is a random read of 512 bytes. Queue depth 1.

Any info much appreciated!

Greg.

 

[sullivang]

I've done further testing.

I first tried the HP SimpleSave drive on my desktop computer - same result.

I then tried a very old ATA drive (in a USB enclosure), and this one does NOT suffer from this problem! I went as high as 20 seconds between each io, and the response time remained very low.

It's looking like it's the drives themselves at this stage. Maybe power saving, or preventative anti-shock head parking, or something?

I've contacted Samsung again and asked them to double check their information. ;^)

Greg.