As SSDs become increasingly common in data centers and consumer PC setups, we’ve seen more questions regarding which SSDs are truly reliable (and under what test conditions). When we last visited this issue, we covered a report on SSD reliability when the drive suddenly loses power, but the report authors didn’t name names or give any information regarding which drives failed more than others. A new report has been released that does name drive manufacturers — and it singles out Intel as the only company whose products didn’t fail under heavy testing.

Before we dive into the results, we need to discuss the conditions of the test. The drives in question were being evaluated for long-term sensor data recording where speed and SSD size were of secondary importance compared to reliability and price. The author states that the drives he tested were chosen based on whether they advertised “Power Loss Protection,” were reliable and inexpensive. This last criteria is somewhat flexible, but provided pricing information indicates a target between £30-£90 ($50-$150 USD).

The drives tested were:

Crucial M4 (128GB)

Toshiba’s THNSNH060GCS (60GB)

Intel S3500

Innodisk 3MP Sata Slim (8GB and 16GB)

Intel’s older 320 SSD (We tested the related SSD 330 in our cache comparison benchmark)

OCZ’s 32GB Vertex SSD

The author of the report, Luke Leighton, tested the following scenarios:

Repeatedly flipping power on and off at the switch (no drives failed this test)

Massively parallel write operations (thousands of directories, millions of small files)

Direct disk writing (tested in a manner similar to the original SSD reliability report).

Results

Just power cycling the drives while no read/write operations were occurring was no problem, but power cycling them during the read-synchronize-write cycle was incredibly problematic. After 1600 power cycles, the M4 was recording up to 40,000 CRC errors. The Toshiba THNSNH060GCS upgrade kit was able to maintain file integrity if file writes were handled at less than 20MB/sec total, even when writing 64 threads of data. Exceed that rate, however, and the Toshiba drive starts losing data quickly.

The Innodisk 3MP SATA Slim kit performed decently in single-thread tests, but performance cratered if more than one thread was run at a time. No errors were reported due to power cycling because the test itself couldn’t run properly — this information has been forwarded to Innodisk, and Luke reports that he’s waiting to hear from the company. As for the OCZ results, they were rather interesting. Equipped with its default firmware, the drive repeatedly failed the massively parallel write test, even with a steady power state. Downgrading the firmware to an older version that wasn’t optimized for higher performance allowed the drive to consistently perform with no errors while the power was on, but still resulted in corruption when the power was interrupted in mid-write.

The Intel drives, in contrast, didn’t fail, despite being power-cycled over 6,500 times. Neither the Intel 320 or the newer S3500 failed to verify the data write in any circumstances.

Limited conclusions, troubling data

Critics have pointed out that the author only tested a small subset of SSDs out of the total market. This is true — but it also drives home the fact that the author was specifically looking for drives with limited storage capability. Drive prices appear to have ranged from $50-$150, which implies a cost of around $6.25 to $9.75 per gigabyte. A 250GB Samsung 840 Evo, in contrast, can be had for under $170. Given that all the tested drives advertised power loss protection, it’s clear that the gap between claims and reality is getting steadily wider.

The implications for the consumer market are uncertain. Unexpected power failures are arguably a greater problem for desktops than laptops, because most laptops are protected by a battery and the OS will automatically manage a graceful shutdown/hibernate period rather than dropping off a cliff when the battery goes dead. It’s also possible that part of the problem here is that SSDs are able to handle massive parallel operations that previous HDDs realistically couldn’t manage outside of massive enterprise installations in RAID arrays with high drive counts and dedicated power supplies. 64-thread tests on a single HDD will bring even the most robust drive to its knees. 64 threads at once on an SSD isn’t as problematic.

One of the problems that these tests highlight is that there’s no simple method of determining which SSDs are and aren’t reliable beyond paying even more inflated prices per gigabyte. Consumers and commercial users would both benefit from a drive program that emphasized and delivered high reliability in edge cases as well as delivering on capacity and cost per gig. The “Buy Intel” recommendation of the original article is worth considering if you need drives that can survive random power outages. Other consumers should seriously consider uninterruptable power supplies (desktops) and make certain your laptop battery doesn’t degrade to the point that it can’t supply the system for at least a few minutes.

Note: At present, only the Intel S3500 and S3700 provide this power protection capability. The Intel 540 series does not.