Hi, by morphin writes: > Hello. > > I'm getting too much bad return from my customers at 4k random speeds. They > claim that SQL databases works much slower than usual, and I can't find a > solution. ...
Not sure if related, but I also observed very strange IO speed behaviour, but did not check it again for long time. Initial observation was, that cryptoloop sometimes was much slower when disk IO was 4k aligned, while sector-aligned but 4k-UNaligned was FASTER. This was unexpected: I assumed to have best speed with 4k IO and 4k memory page size. Drilling it down, it showed that the cryptography stuff did not matter: using a loop with offset only but no cryptography operation showed the same behavior. Also block device IO bus speed was NOT the real cause. Mapping two RAM disks via loop over each other, pure memory page aligned transfer was much SLOWER than 4k-unaligned. Therefore I decided to continue disk partitioning with odd number of 512-byte sectors as 4k alignment reduced the speed, but did not search for the root cause. hd
