Have you done any performance testing with smaller block sizes for SSD partitions?

LinuxAssailant · 12-09-2018, 02:52 AM

With all the slack-space that is wasted, and every SSD I have owned having 512 byte blocks (not emulated, nor 4k), I can't really see a need to use full 4k blocks.

Can someone enlighten my to the drawbacks of smaller blocks if one has 512 byte sectors on their SSDs?

smallpond · 12-10-2018, 03:13 PM

Sectors on an HDD refer to physical sectors of 512 or 4K. SSD sectors are all logical. Erase blocks on SSD range from 128K to 1M or so. The firmware on the drive manages logical sector reads and writes from RAM cache and maps the logical blocks to physical blocks in flash. The main drawback of small sector size is that each sector requires CPU cycles to add it to an I/O list and mark it complete when done, so there is slightly lower CPU overhead for larger block sizes.

LinuxAssailant · 01-15-2019, 08:00 PM

Quote:

Originally Posted by smallpond

Sectors on an HDD refer to physical sectors of 512 or 4K. SSD sectors are all logical. Erase blocks on SSD range from 128K to 1M or so. The firmware on the drive manages logical sector reads and writes from RAM cache and maps the logical blocks to physical blocks in flash. The main drawback of small sector size is that each sector requires CPU cycles to add it to an I/O list and mark it complete when done, so there is slightly lower CPU overhead for larger block sizes.

So the happy place would be 128K blocks?

Seems like a waste of writes.

jefro · 01-15-2019, 09:29 PM

Seems kind of unusual to have that small of writes unless this is a dedicated data disk. ?? dunno