FAQ
Hello again.

Do any of you have one of the 'new' HDDs with 4kB Sectors currently in use?
I would upgrade to the 4kB disks but I don't know if this might be
problematic as I intend to use ZFS w/ RAIDz or at least a classic RAID6.
How might this affect performance under 5.5 and how do I go about setting up
the alignment of the partitions I use?

Kind regards

Dawid Horace

Search Discussions

  • Compdoc at Apr 21, 2011 at 8:40 am

    how do I go about setting up
    the alignment of the partitions I use?

    If you use one large partition it's easy: you just create the partition
    leaving 1 meg of free space before the partition. This causes the partition
    to start at sector 2048, which is a number that 4096 is divisible by. Newer
    versions of disk utilities like gparted suggest this for you by placing a 1
    in the 'Free Space Preceding' box when you go to create a new partition.

    If you create multiple partitions, it's a little harder since you have make
    sure that subsequent partitions start on sectors that can be divided evenly
    into 4096. I've never done this as I always set up one large partition on my
    storage arrays, and I use a separate drive for the OS to boot from and
    another separate drive for my VMs. I do this for performance reasons.

    All of this is explained more or less if you google.
  • Devin Reade at Apr 21, 2011 at 11:17 am
    --On Thursday, April 21, 2011 11:16:36 AM +0200 Dawid Horacio Golebiewski
    wrote:
    Do any of you have one of the 'new' HDDs with 4kB Sectors currently in
    use?
    I have them in use, and set up the partitions manually before installing
    the OS. This is the relevent entry from my server changelog, prior to
    installing CentOS 5.5:

    + since this machine is using new drives with 4k blocks,
    used fdisk to ensure that sector alignment will be sane:

    fdisk -H 224 -S 56 /dev/sd{a,b}

    In doing so, I created a 200MB RAID1 partition (type 0xfd)
    and another RAID1 partition with the remaining disk for use
    by LVM.

    I found it necessary to use fdisk manually on both disks,
    because the following command choked (probably due to
    the geometry thing):

    sfdisk -d /dev/sda | sfdisk /dev/sdb
    (DOESN'T WORK)

    I case it's not obvious, the partitions on sda and sdb are then
    mirrored, the small one for /boot, the large one for the remaining
    filesystems under LVM.

    If you're using the Caviar green drives, beware of excessive head
    park and quickly increasing load cycle counts. I fixed that with
    using an idle timeout of 300 seconds (vice 8 seconds) per:


    <http://community.wdc.com/t5/Desktop/Green-Caviar-High-Load-Cycle-Cout-after-short-operation-time/td-p/15731/page/7>

    Devin

Related Discussions

Discussion Navigation
viewthread | post
Discussion Overview
groupcentos @
categoriescentos
postedApr 21, '11 at 5:16a
activeApr 21, '11 at 11:17a
posts3
users3
websitecentos.org
irc#centos

People

Translate

site design / logo © 2022 Grokbase