On Sat, 12 Mar 2011 11:54:00 +0100 Markus Schatzl <[email protected]> wrote:
> To my understanding, matching the erase block size of SSD > memory can produce a gain in performance, however the most > important thing is to align at 4k boundaries. > > As this is the case, the current (pre 4.9) state in OpenBSD is > handling the setup of SSD disks in the best possible way > automatically. From your replies I conclude that there should be > no additional configuration necessary. For 4KB sector disks the magic number for alignment is multiples of 8. That case has been handled by bumping the offset to 64sec. With SSDs you really wan't to align on erase-blocks or multiples of their size. Most SSDs use 512KB EBs, newer drives are switching to 1MB EBs. (multiples of 1024 or 2048 512byte sectors) If you don't align on EBs you will have higher write amplification. The drive won't last as long. Unaligned you will have to touch 2 blocks instead of one more often, the disk will get slower sooner too; OpenBSD does not support Trim atm. (Talking about "normal" controllers,not about Sandforce like solutions.)
