6 ms·

I work with bioinformatics data and tend to switch out an NVMe within 3-4 months. I'm usually maxing out read or write for 12 out of 24 hours a day. The slowdow

by Blahah 6y ago

I work with bioinformatics data and tend to switch out an NVMe within 3-4 months. I'm usually maxing out read or write for 12 out of 24 hours a day. The slowdown is rapid and very noticeable.

wtallis 6y ago
> The slowdown is rapid and very noticeable. That probably doesn't have anything to do with write endurance of the flash memory. When your drive's flash is mostly worn-out, you will see latency affected as the drive has to retry reads and use more complex error correction schemes to recover your data. But there are several other mechanisms by which a SSD's performance will degrade early in its lifetime depending on the workload. Those performance degradations are avoidable to some extent, and are not permanent.
- Blahah 6y ago
  So I can potentially recycle my used SSDs?
  - mehrdadn 6y ago
    I think you could give it a shot with ATA Secure Erasing one of them and seeing if it performs faster. Although 4 months at 50% utilization at (say) 2GB/s is some ~10PB of I/O, so I'm not sure if I would expect what you're seeing to be a temporary slowdown...
  - wtallis 6y ago
    Almost certainly. Assuming these are consumer SSD, the most important way to maintain good performance is to ensure that it gets some idle time. Consumer SSDs are optimized for burst performance rather than sustained performance, and almost all use SLC write caching. Depending on the drive and how full it is, the SLC cache will be somewhere between a few GB up to about a fourth of the advertised capacity. You may be filling up the cache if you write 20GB in one shot, but the drive will flush that cache in the background over the span of a minute or two at most if you don't keep it too busy. The other good strategy to maintain SSD performance in the face of a heavy write workload is to not let the drive get full. Reserving an extra 10-15% of the drive's capacity and simply not touching it will significantly improve sustained write speeds. (Most enterprise SSD product lines have versions that already do this; a 3.2TB drive and a 3.84TB drive are usually identical hardware but configured with different amounts of spare area.) If a drive has already been pushed into a degraded performance state, then you can either erase the whole drive or, if your OS makes proper use of TRIM commands, you can simply delete files to free up space. Then let the drive have a few minutes to clean things up behind the scenes.

by Blahah 6y ago

I work with bioinformatics data and tend to switch out an NVMe within 3-4 months. I'm usually maxing out read or write for 12 out of 24 hours a day. The slowdown is rapid and very noticeable.

wtallis 6y ago

> The slowdown is rapid and very noticeable. That probably doesn't have anything to do with write endurance of the flash memory. When your drive's flash is mostly worn-out, you will see latency affected as the drive has to retry reads and use more complex error correction schemes to recover your data. But there are several other mechanisms by which a SSD's performance will degrade early in its lifetime depending on the workload. Those performance degradations are avoidable to some extent, and are not permanent.

Blahah 6y ago
So I can potentially recycle my used SSDs?
- mehrdadn 6y ago
  I think you could give it a shot with ATA Secure Erasing one of them and seeing if it performs faster. Although 4 months at 50% utilization at (say) 2GB/s is some ~10PB of I/O, so I'm not sure if I would expect what you're seeing to be a temporary slowdown...
- wtallis 6y ago
  Almost certainly. Assuming these are consumer SSD, the most important way to maintain good performance is to ensure that it gets some idle time. Consumer SSDs are optimized for burst performance rather than sustained performance, and almost all use SLC write caching. Depending on the drive and how full it is, the SLC cache will be somewhere between a few GB up to about a fourth of the advertised capacity. You may be filling up the cache if you write 20GB in one shot, but the drive will flush that cache in the background over the span of a minute or two at most if you don't keep it too busy. The other good strategy to maintain SSD performance in the face of a heavy write workload is to not let the drive get full. Reserving an extra 10-15% of the drive's capacity and simply not touching it will significantly improve sustained write speeds. (Most enterprise SSD product lines have versions that already do this; a 3.2TB drive and a 3.84TB drive are usually identical hardware but configured with different amounts of spare area.) If a drive has already been pushed into a degraded performance state, then you can either erase the whole drive or, if your OS makes proper use of TRIM commands, you can simply delete files to free up space. Then let the drive have a few minutes to clean things up behind the scenes.