X-bit labs

Western Digital Passport Mobile Hard Disk Drive with 250GB Storage Capacity (page 4)

Category: Storage

by Aleksey Meyev

[ 09/05/2007 | 02:31 PM ]

Database Pattern

In the Database pattern the drive is processing a stream of requests to read and write 8KB random-address data blocks. The ratio of read to write requests is changing from 0% to 100% throughout the test: in the beginning of the tests the reads are at 100%, while at the ends the writes hit 100%.

Let’s take a look at three diagrams showing the dependence of the HDD performance on the read-to-write request ratio under three types of workload: 1, 16 and 256 outgoing requests in the queue.

In case of 1 request queue as the share of writes increases, so does the Passport 250GB performance per second. Looks like the new hard drive learned to work efficiently with lazy writing, which we haven’t seen by USB devices before. In most cases, USB devices like that perform similarly to the Passport 120GB. As a result, Passport 250GB performs great when write requests dominate, and is just a little ahead during reads.

As the number of requests in the queue increases to 16, we see that the newcomer demonstrates much higher number of operations per second when read requests dominate the ratio. And again we don’t see the graph for the 250GB model to drop in the center part, which is typical of the external USB solutions. The 120GB model has a very vivid demonstration of this phenomenon.

When the queue hits 256 requests, the left side of Passport 250GB graphs rises even more, so that we notice a slight curve in the center. With any read-to-write ratio, the new solution outperforms its predecessor, but the difference is especially noticeable in the center of the graph, where Passport 120GB runs at its minimal speed.