On Friday 03 April 2015 20:22:18 Chris Bannister wrote: > On Fri, Apr 03, 2015 at 05:39:32PM -0400, Gene Heskett wrote: > > Usually less than 4 megabytes of free space left at the end of the > > disk with a used 4k per sector disk on the cable, but could be zero > > for a 512 byte per sector used disk since there is not normally an > > alignment problem with the old 512 byte per sector formatting. I > > have 1Tb disks that look alike at first glance. The 512 byte per > > sector pair is heavier and a wee bit thicker because it likely has > > two platters in it, while the 4k version pair is a bit lighter and > > thinner, I presume because there is only one platter in those two > > disks. > > > > The commodity drives I have coming will be, at 2Tb, 4096 bytes per > > sector, and linux must align its writes with a Read-Modify-Write > > cycle updating the whole 4k just to change one byte if things don't > > start on a sector boundary. There's a pretty good speed penalty for > > doing that. A disk that can write at 120+ megs a second when aligned > > can be turned into a 20 megs a second slowpoke. if miss-aligned. > > Ahh!, weren't you mentioning performance problems? > > There was a recent discussion on the netbsd-users list about 4k disks. > > In particular this: > http://mail-index.NetBSD.org/netbsd-users/2015/03/27/msg015986.html
Bootability doesn't seem to be a problem unless I try to boot a kernel so old it has no clue what to do with this disk: (from sudo smartctl -a /dev/sda) >Sector Sizes: 512 bytes logical, 4096 bytes physical No clue but following a suggestion, the first partition actually starts 4 mebibytes into the disk, which seems to guarantee proper alignment with the physical sectors. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: https://lists.debian.org/[email protected]
