The traditional view is that solid-state drives themselves are less prone to failure than mechanical hard drives because they have no moving parts. But it turns out that a new report from Backblaze shows that there are rotating disks, actuator arms, and motors in all HDDs, which may not be a big disadvantage because it is related to reliability.
Backblaze is a subscription-based cloud storage and backup service that has been running for more than ten years. Therefore, it is in a unique position to provide real-world data on drive failure rates, and it often provides statistics on its drive failures for public use.
The company had only used HDDs until mid-2018, when it began trialling SSDs as boot drives. The experiment went well, so it ended up switching to only using SSD as the boot drive in new storage deployments, and when replacing failed HDDs.
“In our example, it is a misnomer to describe these drives as boot drives, because boot drives are also used to store log files for system access, diagnostics, etc. In other words, these boot drives regularly read and write And deleting files is in addition to their naming function to start the server at startup,” Backblaze explained.
This allows Backblaze to compare failure rates From 1,666 SSDs to 1,607 HDDs, and the initial data is biased towards the latter-since the deployment of fast storage media, only 17 SSDs have failed, while HDDs have failed 619.
At first glance, SSDs seem to be much more reliable than HDDs. However, Backblaze pointed out that the average lifespan of SSD drives is only 14.2 months, and the oldest of them has been in use for 33 months.At the same time, the average age of hard drives is 52.4 months, of which The youngest 27 months.
“In order to create a more accurate comparison, we can try to control the average age and driving days in our analysis. To this end, we can retrieve the HDD group in our records in time to see where the average age and driving days are similar SSD in the second quarter of 2021,” Backblaze said.
This is what it looks like when controlling the age of the drive:
Most hard disk failures occur after a long period of time. When looking back about the drive failures about 14 months later, the failure rate of SSDs was still low, but not many—their annual failure rate was 1.05%, compared with 1.38% for HDDs.
“This allows us to choose between buying an SSD or an HDD? Given what we know so far, using failure rates in your decision is questionable,” Backblaze said. “Once we control the service life and drive days, the two drive types are similar, and the difference itself is certainly not enough to justify the additional cost of buying SSDs and HDDs.”
This does not mean that you should reuse the HDD. Backblaze emphasized several other determinants, such as speed, power, and form factor requirements (or preferences).
It is also worth noting that the data range is limited. Although the early failure rate is not very beneficial to SSD compared to HDD, it is entirely possible that SSD will prove to be more reliable over time. Only time will give the answer. In addition, not all drives are created equal. Although it is still interesting, the data is too narrow.
In other words, all SSD failures are not the result of write endurance or SMART monitoring statistics. Backblaze stated that it is only beginning to use SMART stats to proactively fail the SSD, which means that if it thinks that the failure is imminent, it will yank the SSD. These are reactive faults, the drive just stops working.