On 15/02/13 12:40, Chris Murphy wrote: > > On Feb 14, 2013, at 6:10 PM, Adam Goryachev > <mailinglists@xxxxxxxxxxxxxxxxxxxxxx> wrote: >> >> So assuming I don't mind wasting a few MB per disk (I was leaving >> empty space at the end of the partition anyway), what would I need >> to instruct fdisk and/or md to do to get the alignment right? >> >> Current partition/disk is as follows: /dev/sdc1 63 >> 931769999 465884968 fd Lnx RAID auto > > Yeah the old fdisk starts at LBA 63 which is not good because it's > neither 4K nor 8K aligned. For a long time now fdisk starts new ones > at 2048 which is 1MB aligned (and is of course also 8KB and 4KB > aligned, among others so it's just easier to do that.) But for 4K and > 8K alignment, start LBA 48, 64, 80, etc are also valid. Probably a stupid question, but how do I force fdisk to start at 64 ? or even 2048? Would it be a sequence like this: fdisk /dev/sdb d <- delete the existing partition u <- change units n <- new partition p <- primary 1 <- partition 1 64 <- start sector 64 xxx <- end size of partition Will that make it right? I'm planning on doing: mdadm --manage /dev/md0 --fail /dev/sdb1 mdadm --manage /dev/md0 --remove /dev/sdb1 fdisk (delete and re-create partition, same size, different start/end) mdadm --manage /dev/md0 --add /dev/sdb1 Wait for resync to complete, and repeat with the next disk. I was thinking to also use smartctl to instruct the disk to do a format before creating the new partition. Would that help to "trim" the disk, or not make any difference at all (since md will re-write the whole disk in the resync phase anyway). Thanks, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
