On Sat, Aug 25 2012, Frank Steinmetzger wrote: > On Sun, Aug 26, 2012 at 12:22:47AM +0200, Volker Armin Hemmann wrote: > >> > > The size of an erasable block of SSDs is even larger, usually 512K, it >> > > would be best to align to that, too. A partition offset of 512K or 1M >> > > would avoid this. >> > >> > Unless the filesystem knows this and starts bigger files at those 512 k >> > boundaries (so really only one erase cycle is needed for files <=512 k), >> > isn't this fairly superfluous? >> >> no, if you misalign, a lot of 4k blocks might span into two erase blocks. >> Which is bad. If you align correctly, you will never cross them >> unnecessary, >> sparing your SSD some unnecessary writes and improving overall performance. > > I don’t quite follow. If you align to 4k, then you are also aligned to 512k, > because 512 % 4 = 0.
Backwards. Consider starting at 8K. This is a multiple of 4K but is not a multiple of 512K. If you align to 512k than you are also aligned to 4k because 512 % 4 = 0. allan
