Am Sonntag, 26. August 2012, 13:41:09 schrieb Alex Schuster: > Frank Steinmetzger writes: > > On Thu, Aug 23, 2012 at 12:15:20PM +0200, Alex Schuster 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? > > Yes, I think it is. When you search for SSD alignment, you read about > this alignment all the time, even on the German Wikipedia, and many > resources say that this can have a big impact on performance. But I > could not find a real explanation at all. > > Besides that, it's not so easy to do the alignment, at least when using > LVM. I read that LVM adds 192K header information, so even if you align > the partition start to an erasable block size of 512K, the actual > content is not aligned. See [*] for information how to overcome this. > That is, if you believe the alignment to erasable blocks is important, > personally I do not know what to think now. It wouldn't hurt, so why not > apply it, but it seems like snake oil to me now. > > Wonko > > http://tytso.livejournal.com/2009/02/20/
because erasing is slow. You can not overwrite data on a ssd. you have to erase first, then reprogramm. Also, erasing shortens lifetime. -- #163933
