Western Digital sells three models of hard drives with similar model numbers: WD10EADS (32 MiB cache), WD10EACS (16 MiB cache), and WD10EAVS (8 MiB cache). The last of these is intended to be sold to OEM manufacturers, but you can buy an individual unit from various sources as long as you don't mind the lack of a warranty. I picked one up for $70.
I had expected the performance of all three of these models to be basicly the same, but it turns out that that's not quite right. The following table shows the sequential read speeds (in millions of bytes per second) at the beginning, middle, and end of each disk.
94.2 77.9 44.9 WD10EAVS
98.7 83.7 46.1 WD10EACS
126.3 109.2 66.0 ST3500410AS
The WD10EAVS is slightly slower than my WD10EACS. As you would expect, both are significantly slower than my 7200 RPM Seagate ST3500410AS drive.
Sequential read speed is not a particularly good indicator of how a drive will perform in actual usage, so I decided to use a search of the Linux kernel source as a benchmark. I created a copy of my /usr/src partition on each drive and ran the following command on the Linux kernel source:
find . -type f -name '*.[ch]' -print | xargs fgrep -l raid_setupx
On POSIX systems, when a file is read the access time of the file is updated, but Linux allows the update to be turned off in order to increase performance. The following table shows the run time of the command, in seconds. The second column gives times with updates of access times turned off:
44.2 42.9 WD10EAVS
33.3 32.6 WD10EACS
33.6 33.1 ST3500410AS
36.0 34.6 WD10EAVS/WD10EACS/ST3500410AS raid 5
On this benchmark, the WD10EAVS takes about 32% longer than the WD10EACS. The latter performs quite well, basicly matching the performance of the Seagate drive. The Seagate had a slight advantage because the file system was closer to the start of the drive on the Seagate disk than it was on the other disks. The last line shows the performance with all three disks combined into a RAID 5 configuration.
The WD10EADS/WD10EACS/WD10EAVS disks are "green" disks, so you probably aren't looking at these if performance is paramount. Still, the performance numbers suggest that the WD10EAVS should be avoided if you can get one of the other models for a similar price.
(Notes: To obtain the numbers in the above tables, I ran each test 9 times and selected the median. For the second set of tests, I unmounted the file system and did a raw disk copy. Copying the files rather than the disk could result in the files being laid out on disk differently, resulting in a meaningless comparison. The tests were run using a Gigabyte GA-MA790XT-UD4P motherboard, with an AMD Phenom II X3 710 processor overclocked to 3250 Mhz, and 2 GiB of DDR3-1333 memory.)
I had expected the performance of all three of these models to be basicly the same, but it turns out that that's not quite right. The following table shows the sequential read speeds (in millions of bytes per second) at the beginning, middle, and end of each disk.
94.2 77.9 44.9 WD10EAVS
98.7 83.7 46.1 WD10EACS
126.3 109.2 66.0 ST3500410AS
The WD10EAVS is slightly slower than my WD10EACS. As you would expect, both are significantly slower than my 7200 RPM Seagate ST3500410AS drive.
Sequential read speed is not a particularly good indicator of how a drive will perform in actual usage, so I decided to use a search of the Linux kernel source as a benchmark. I created a copy of my /usr/src partition on each drive and ran the following command on the Linux kernel source:
find . -type f -name '*.[ch]' -print | xargs fgrep -l raid_setupx
On POSIX systems, when a file is read the access time of the file is updated, but Linux allows the update to be turned off in order to increase performance. The following table shows the run time of the command, in seconds. The second column gives times with updates of access times turned off:
44.2 42.9 WD10EAVS
33.3 32.6 WD10EACS
33.6 33.1 ST3500410AS
36.0 34.6 WD10EAVS/WD10EACS/ST3500410AS raid 5
On this benchmark, the WD10EAVS takes about 32% longer than the WD10EACS. The latter performs quite well, basicly matching the performance of the Seagate drive. The Seagate had a slight advantage because the file system was closer to the start of the drive on the Seagate disk than it was on the other disks. The last line shows the performance with all three disks combined into a RAID 5 configuration.
The WD10EADS/WD10EACS/WD10EAVS disks are "green" disks, so you probably aren't looking at these if performance is paramount. Still, the performance numbers suggest that the WD10EAVS should be avoided if you can get one of the other models for a similar price.
(Notes: To obtain the numbers in the above tables, I ran each test 9 times and selected the median. For the second set of tests, I unmounted the file system and did a raw disk copy. Copying the files rather than the disk could result in the files being laid out on disk differently, resulting in a meaningless comparison. The tests were run using a Gigabyte GA-MA790XT-UD4P motherboard, with an AMD Phenom II X3 710 processor overclocked to 3250 Mhz, and 2 GiB of DDR3-1333 memory.)