Analysis of SSD Reliability during power-outages
This report was originally commissioned due to the remote deployment of over 200 32GB OCZ SSDs resulting in severe data corruption in over 50% of the units. The recovery costs were far in excess of the costs saved by purchasing the cheaper OCZ units. They were replaced rapidly over a period of years by Intel SSD 320s, where, despite remote deployment of over 500 units there have only ever been three unrecoverable failures.
However, the Intel 320 SSD has reached end-of-life, so a replacement was sought. Due to paranoia over the OCZs an in-depth analysis was requested. Around the time that the paranoia was hitting, a report had come out on slashdot, covering power-related corruption.
It made sense therefore to attempt to replicate that report, as it was believed that the data corruption of the OCZs was related to power loss.
This report therefore covers the drives selected and the testing that was carried out. We follow up with a conclusion (summary: if you care about power loss don't buy anything other than Intel SSDs - end of story) and some interesting twists. Picking drives for testing
The scenario for deployment is one where huge amounts of data simply are not required. An 8GB drive would be able to store 1 month's worth of sensor data, as well as have room for a 1.5GB OS deployment. A 16GB drive stores over two months. Bizarrely, except in the Industrial arena the focus is on constant increases in data storage capacity rather than data reliability. The fact that shrinking geometries automatically results in higher susceptibility to data corruption is left for another time, however.
Additionally, due to the aforementioned paranoia and assumptions that the data loss was occurring due to loss of power, the requirements to have "Power Loss Protection" were made mandatory. Power Loss Protection is usually found in Industrial and Server Grade SSDs, which are typically more expensive.
So, finding low-cost low-size reliable SSD reported to have "Power Loss Protection" proved... challenging. After an exhaustive search, the following candidates were found:
- Crucial M4 128GB
- The unpronounceable Toshiba THNSNH060GCS 60GB
- The new Intel S3500
- The Innodisk 3MP SATA Slim (8GB and 16GB)
The Innodisk units came in around £30, whilst all the other drives came in at between £60 and £90. Also added to the testing was the original 32gb Vertex OCZ and the Intel 320.