Review: Hard disk vs. solid-state drive -- is an SSD worth the money?

SSDs have the speed, but HDDs have the capacity

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The Vertex is OCZ's second iteration of an SSD, and it uses 64MB of cache to artificially enhance the write performance and a more advanced Indillinx controller than its slower predecessor, the OCZ Apex Series SSD, which uses a controller from JMicron and has no cache memory. The Vertex drive's packaging lists a maximum read rate of 250MB/sec and a sustained write rate of 100MB/sec. It also claims a 1.5 million-hour mean time between failure (MTBF) rate, if MTBF can actually be applied accurately to an SSD. Most experts don't believe it can.

(Keep in mind that most SSD vendors publish sequential read/write rates, which are much faster than random I/O. But most operations on a desktop or laptop are random. For example, file systems and e-mail applications mostly use random operations, while system boot up or copying a large file from a USB drive involves sequential operations. So, in general, don't believe the packaging hype.)

The Seagate Momentus 7200.4 marketing material offers no read/write rates, nor does Seagate offer any information other than a seek time on its Web site: 11 milliseconds for reads and 13 milliseconds for writes. Seagate doesn't use MTBF, preferring its own annualized failure rate (AFR) metric as a method to gauge drive reliability, which is .5%.

The SSD easily beats the HDD in weight. Seagate's Momentus weighs 3.85 ounces; OCZ's drive weighs 2.7 ounces.

Performance tests

Not surprisingly, the Vertex SSD handily beat the Seagate HDD for cold boots: 20 seconds to start up Windows XP for the OCZ and 40 seconds for the Seagate. The SSD also beat the HDD for restarts: 26 seconds versus 37 seconds.

(While it may seem odd that the Seagate drive performed better on a restart than on a cold boot, keep in mind that the drive is still spinning and plenty of OS data is still residing in memory. The drive also has native command queuing (NCQ), which allows its controller to prefetch data in order to access it more quickly on reboots. It works in the same way a grocery list helps you find products as you enter the store. OCZ's Vertex drive with Indillinx controller also has NCQ.)

When it came to I/O speed, there was no match. I used ATTO Technology's ATTO Disk Benchmark v2.3.4 and Simpli Software's HD Tach v3.0.4 benchmarking utilities to perform my read/write performance tests. The ATTO benchmark software showed the OCZ had a read time of 244MB/sec and a write time of 172MB/sec. The Seagate HDD had an average read rate of 98MB/sec and a write time of 87MB/sec.

The Seagate HDD was no match for the SSD for I/O
ATTO's benchmarking software test results for the Seagate 500GB Momentus HDD
The Seagate HDD was no match for the SSD for I/O
ATTO's benchmarking software test results for the OCZ Vertex 120GB SSD

Using HDTach, the read/write results were quite different. OCZ's drive showed a 196MB/sec read rate, the Seagate, 84.6MB/sec.

The HDTach software also measures CPU utilization and random access times. OCZ's drive had a random access time of .2 milliseconds; Seagate's 16.9 milliseconds. While Seagate's slower random access time wasn't surprising, I was surprised that it actually beat the OCZ drive on CPU utilization: the OCZ SSD used 8%; the Seagate HDD used 5%.

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