We weren’t satisfied that only a relatively small number of volumes and customers had better performance. We wanted to bring the benefits of SSDs to everyone. This is an area where scale makes things difficult. We had a large fleet of thousands of storage servers running millions of non-provisioned IOPS customer volumes. Some of those same volumes still exist today. It would be an expensive proposition to throw away all of that hardware and replace it

The larger the capacity of an SSD, the more data can be written to it during its working life.

If you know the TBW for an SSD and the total amount of data that has been written to it during its lifetime, it’s simple to estimate the percentage of its lifetime (as TBW) that has been used up, hence the amount remaining.

the logical and physical page addresses are decoupled. A mapping table, which is stored on the SSD, translates logical (software) addresses to physical (flash) locations. This component is also called Flash Translation Layer (FTL).

NAND flash pages cannot be overwritten. Page writes can only be performed sequentially within blocks that have been erased beforehand.

For example, if one looks at write latency, one may measure results as low as 10us – 10 times faster than a read. However, latency only appears so low because SSDs are caching writes on volatile RAM. The actual write latency of NAND flash is about 1ms – 10 times slower than a read.

Another important difference between disks and SSDs is that disks have one disk head and perform well only for sequential accesses. SSDs, in contrast, consist of dozens or even hundreds of flash chips ("parallel units"), which can be accessed concurrently.

SSDs are often referred to as disks, but this is misleading as they store data on semiconductors instead of a mechanical disk.

Jan 2021. I use a small, dedicated enterprise grade SSD as a swap drive. These enterprise drives can be bought for as little as $80 for 240GB right now, and are 3D nand with load leveling and other valuable improvements for swap. By using the drive only for swap, you pretty much guarantee it won’t affect your expensive terabyte level data drive should it fail, and you still get the performance of SSD. Estimates for very heavy use are about 2 1/2 years.

T40 with SATA SSD and SATA->IDE bridge anyone?

echo 1 > /sys/block/(whatever)/device/delete