Why my 15K SAS HDD drives are so slow? [closed]

Question

I have a DELL PE2950 III 2x 3.0GHz Quad Core 32GB RAM.

The card is a Perc 6i SAS dual channel Raid controller w/256mb of cache and BB. The hard disks are

• 5 x 146GB 15k 3G SAS dell drives ST3146855SS working independent

testing with hdparm I see the following:

/dev/sdb1:
 Timing cached reads:   3858 MB in  2.00 seconds = 1930.17 MB/sec
 Timing buffered disk reads: 378 MB in  3.01 seconds = 125.39 MB/sec
/dev/sdc1:
 Timing cached reads:   3582 MB in  2.00 seconds = 1792.46 MB/sec
 Timing buffered disk reads: 374 MB in  3.01 seconds = 124.06 MB/sec*

But with a desktop computer with 7.2k seagate baracuda I see:

/dev/sdb1:
 Timing cached reads:   12050 MB in  2.00 seconds = 6028.07 MB/sec
 Timing buffered disk reads: 418 MB in  3.01 seconds = 138.93 MB/sec*

So the question Why do I have so low speed?

Answer 1

The sustained read specification for this drive is 125MB/s You're getting 124-125MB/s. So you're right where you should be.

Up to 125-MB/s sustained transfer rate -- Ad

The Barracudas have a higher sustained transfer rate due to their higher areal density but also a slightly higher latency due to their lower spin rate (it takes longer for the data to "come around" to the head).