FAQ
CentOS Community,

It is to my understanding that the /boot partition should never be
placed on LVM and should be a physical partition on the hard drives
(or on top of a RAID array). Is this an accurate statement?

Also please advise if the SWAP filesystem is safe to be placed under
LVM, or if this should be a hard partition / hard limit as well. I am
unsure if boot issues or any filesystem issues would be caused by
placing them on LVM. Please educate me if possible.

Thanks in advance for the information!

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  • Muhammad Panji at Jan 16, 2012 at 10:38 pm

    On Tue, Jan 17, 2012 at 10:26 AM, Jonathan Vomacka wrote:

    CentOS Community,

    It is to my understanding that the /boot partition should never be
    placed on LVM and should be a physical partition on the hard drives
    (or on top of a RAID array). Is this an accurate statement?
    Yup. Because GRUB < 1.95 cannot read it
    http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-lvm-diskdruid-manual.html

    Also please advise if the SWAP filesystem is safe to be placed under
    LVM, or if this should be a hard partition / hard limit as well. I am
    unsure if boot issues or any filesystem issues would be caused by
    placing them on LVM. Please educate me if possible.
    The default partition from anaconda put the swap on LVM so I think that
    wouldn't be a problem.
    even if you need more swap you can make (additional) swap file.
    Regards,
  • Jonathan Vomacka at Jan 16, 2012 at 10:53 pm

    On Mon, Jan 16, 2012 at 10:38 PM, Muhammad Panji wrote:
    On Tue, Jan 17, 2012 at 10:26 AM, Jonathan Vomacka wrote:

    CentOS Community,

    It is to my understanding that the /boot partition should never be
    placed on LVM and should be a physical partition on the hard drives
    (or on top of a RAID array). Is this an accurate statement?
    Yup. Because GRUB < 1.95 cannot read it
    http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-lvm-diskdruid-manual.html

    Also please advise if the SWAP filesystem is safe to be placed under
    LVM, or if this should be a hard partition / hard limit as well. I am
    unsure if boot issues or any filesystem issues would be caused by
    placing them on LVM. Please educate me if possible.
    The default partition from anaconda put the swap on LVM so I think that
    wouldn't be a problem.
    even if you need more swap you can make (additional) swap file.
    Regards,






    --
    -----
    Muhammad Panji
    http://www.panji.web.id ? ? ? ? ? ? ? ? ? ? ? ? http://www.kurungsiku.com
    http://sumodirjo.wordpress.com ? ? ? ? ?http://www.kurungsiku.web.id

    http://www.linuxbox.web.id
    _______________________________________________
    CentOS mailing list
    CentOS at centos.org
    http://lists.centos.org/mailman/listinfo/centos
    Okay, So I guess it is safe to say that SWAP can be placed on LVM but
    /boot can not? /boot should be made with EXT3 i assume, correct?
  • Gordon Messmer at Jan 17, 2012 at 12:48 pm

    On 01/16/2012 07:38 PM, Muhammad Panji wrote:
    even if you need more swap you can make (additional) swap file.
    Swap files are just *awful*. Performance when swapping is bad enough,
    but going through the filesystem layer means updating atime and mtime on
    reads and writes. Things get real ugly with swap files.
  • Steve Thompson at Jan 17, 2012 at 8:40 am

    On Mon, 16 Jan 2012, Jonathan Vomacka wrote:

    It is to my understanding that the /boot partition should never be
    placed on LVM and should be a physical partition on the hard drives
    (or on top of a RAID array). Is this an accurate statement?
    /boot on LVM is quite safe as long as it is below 2GB. Hopefully it is.
    Also please advise if the SWAP filesystem is safe to be placed under
    LVM, or if this should be a hard partition / hard limit as well.
    Swap on LVM is quite safe; in fact it is desired.

    -s
  • Aslan Carlos at Jan 17, 2012 at 9:31 am

    On 01/17/2012 11:40 AM, Steve Thompson wrote:
    on LVM is quite safe as long as it is below 2GB
    It's not possible put /boot on LVM when you working with GRUB.

    Grub works with 2 stages:

    1? - MBR ( Master Boot Record ) , with instruction to access the
    partition where store kernel , initrd and grub.conf
    2? - Reads the partition indicated on 1? stage (MBR), to read grub.conf
    with all instruction to boot the OS.

    Now the question why we cannot use /boot on LVM. LVM is a Logical Volume
    Manager, GRUB no have support yet to read LVM. You'll see this LVM
    structure after the kernel boot and load the LVM modules.

    You could see what filesystems are support by Grub access your /boot
    after installation, looking into /boot/grub.

    Only Grub version 2 could access partitions /boot with LVM. ( I find
    this information now )


    -

    You'll not have problem using SWAP on LVM, but we need think about all
    situations.
    If you running some software that use too much SWAP area, recommend you
    put your SWAP on the firsts primary partition on your disk, because
    there are area more fast I/O. If you want know more about that looking
    for about ZCAV. (This is applicable to electrical mechanical disk, no
    Solid State Disks,SSD).
    Let's think you need more SWAP space, but your using SWAP on LVM, you
    could create a new LVM and add to SWAP area.
    swapon -s (you could see information how many swap partition or files
    you have and how much is the use of them)



    best regards,
    --aslan
  • Gordon Messmer at Jan 17, 2012 at 12:45 pm

    On 01/16/2012 07:26 PM, Jonathan Vomacka wrote:
    It is to my understanding that the /boot partition should never be
    placed on LVM and should be a physical partition on the hard drives
    (or on top of a RAID array). Is this an accurate statement?
    Not necessarily "never" but not if your boot loader is GRUB 0.95.

    /boot should be on a regular partition or an MD RAID1 partition on
    storage that is available to the BIOS (single drive or RAID volume on a
    controller with a boot ROM).

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