WD Caviar Black WD7501AALS 750GB seems slow...

graysky · Post by **graysky** » Sat Mar 28, 2009 2:50 am

I just bought a Western Digital Caviar Black WD7501AALS 750GB (SATAII, 7200 RPM, 32 Mb cache). I ran a few disk benchmarks on it and found that is seems pretty darn slow compared to my Seagate drives. Does anyone else have this WD drive and would you mind running HD Tach on it if you run windows or hdparm if you run LINUX and report the results.

Here are the results using HD Tach under XP Pro 64-bit:
Random access: 14.3ms
Average read: 89.6 MB/s
Burst Speed 224.9 MB/s

Here are the results under LINUX using hdparm
# hdparm -Tt /dev/sda
/dev/sda:
Timing cached reads: 13500 MB in 2.00 seconds = 6761.12 MB/sec
Timing buffered disk reads: 244 MB in 3.02 seconds = 80.92 MB/sec

As a comparison, I ran the same two benchmarks on my Seagate ST3750330AS (also 750 Gb, 7200 RPM, 32 Mb cache):

Here are the results using HD Tach under XP Pro 64-bit:
Random access: 12.9ms
Average read: 91.4 MB/s
Burst Speed 247.6 MB/s

Here are the results under LINUX using hdparm
# hdparm -Tt /dev/sda
/dev/sda:
Timing cached reads: 15880 MB in 2.00 seconds = 7952.77 MB/sec
Timing buffered disk reads: 344 MB in 3.01 seconds = 114.19 MB/sec

dhanson865 · Post by **dhanson865** » Sat Mar 28, 2009 6:29 am

Welcome to the terrible secret of hard drives.

If you had bought the wd6401AALS you would have ended up with a faster drive.

The 640GB version has two 320GB platters. The 750GB version is three 250GB platters. More platters equals more vibration, more power, more heat, more noise, and in this case slower transfer rates due to the difference in areal density.

http://www.wdc.com/en/library/sata/2879-701276.pdf shows the differences between the wd6401aals and wd7501aals.

Notice these items that show the 640GB drive being better:

Sustained transfer rate
Drive ready time
Power usage
non operating shock rating
seek noise

graysky · Post by **graysky** » Sat Mar 28, 2009 2:52 pm

Great info, thanks for the reply.