Western Digital Caviar Green 2TB Hard Drive Review

IOMETER

IOMeter is heavily weighted towards the server end of things, and since we here at HWC are more End User centric we will be setting and judging the results of IOMeter a little bit differently than most. To test each drive we ran 5 test runs per HDD (1,4,16,64,128 que depth) each test having 8 parts, each part lasting 10 min w/ an additional 20 second ramp up. The 8 subparts were set to run 100% random, 80% read 20% write; testing 512b, 1k, 2k,4k,8k,16k,32k,64k size chunks of data. When each test is finished IOMeter spits out a report, in that reports each of the 8 subtests are given a score in I/Os per second. We then take these 8 numbers add them together and divide by 8. This gives us an average score for that particular queue depth that is heavily weighted for single user environments.

Please Note: We have removed all Solid State Drive results from this chart as they tend to compress all hard drive results into a flat smear at the bottom of the chart. This is the only test where SSD results will not be shown in a Hard Disk Drive review.


As with many hard drives on the market today, the Western Digital Caviar Green 2TB prefers deep que depths. However, and unlike the performance models we have seen in the past the Green does peak before the que depth does. This is not due to the fact that it is only a single controller based unit as the Western Digital VelociRaptor is a single controller unit as well. The reason for this is much simpler: this drive has an extremely high random latency and has a relatively slow spindle speed.

All this comes as no surprise as this drive has not been designed (even in the designers dreams…or worst nightmares) as a server grade storage device so the chances of it ever seeing que depths beyond four (and most likely one or two to be honest) are slim. .

IOMeter Stutter Test

In our usual IOMeter test we are trying to replicate real world use where reads severely outnumber writes. However, to get a good handle on how well a given drive will handle a worse case scenario we have also run an additional test. This test is made of 1 section at que depth of 1. In this test we ran 100% random. 100%writes of 4k size chunks of information. In the .csv file we then found the Maximum Write Response Time. This in ms is worst example of how long a given operation took to complete. We consider anything higher than 333ms (one third of a second) to be a good indicator that stuttering may happen, with the higher the number the worse the duration of the stutter will most likely be.


While we usually don’t include the “Stutter” test for hard drives, as this is mainly a Solid State Drive issue (or was) we think it was worthwhile to see how long it really takes for a totally random string of writes to happen. While the average is higher than the other hard drives tested it still was decent, what was concerning was the maximum numbers this drive posted. In fact, this is probably the best example of how hobbled this single controller, single actuator, high latency drive is as the Caviar Green posted maximum numbers usually reserved for Solid State Drives. With that being said, and to be totally fair and balanced, they are still below the no man’s zone of 333ms where stuttering can happen.