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  1. #1
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    Linux Storage Server Partitioning Advice

    Linux Storage Server Partitioning Advice

    We are puting together a Linux Storage server which will have 4 x 1TB SATA Hard Drives connected to Hardware raid configured at level 10.

    We plan to use this box initially for NFS services but in the near future iSCSI targets so would like to make a setup optimal the first time.

    What is the best way to layout the drive partition’s for this setup?
    My thought is

    -100MB /boot ext3
    -Rest in LVM
    --LVM Group
    ---LVM001 2048MB SWAP
    ---LVM002 10GB /
    ---LVM003 500GB /nfs
    ---LVM004 500GB /iscsi

    Is this an efficient setup and provide a great deal of flexibility down the road? We will end up having more than one iscsi target running on this box in the end. Also does LVM experience a performance hit ?
    Last edited by ctnetadmin; 08-13-2009 at 04:39 PM.

  2. #2
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    I've never setup a storage array that did NFS and iSCSI. What iSCSI daemon where you going to use? I use the iSCSI Project. I did use LVM, and performance was fine.

  3. #3
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    Here's my advice. The RAID-10 disk, let's call it /dev/sda, is going to have two partitions. One is /dev/sda1 with 100MB disk space and assigned to /boot as ext3. The rest is going to be assigned to /dev/sda2 as an LVM group. Create your regular root, swap, and other system logical volume partitions.

    Create one logical volume (lvcreate) with the smallest amount of disk space. That's going to be the NFS volume, let's call nfs_lv. Remember that LVM lets you resize partitions as you need to grow them. Also ext3 partitions can be resized online now (no need to umount,fsck, resize2fs, remount).

    Your iSCSI LUNs are going to be LVM partitions. For example,

    lvcreate -L10G -n iscsi_lv_01 /dev/vg
    lvcreate -L10G -n iscsi_lv_02 /dev/vg
    lvcreate -L10G -n iscsi_lv_03 /dev/vg
    You're going to be exporting those luns out to your initiators and then mkfs.ext3 on them. The reason I only allocated 10G is because you can always grow them on the target using

    lvcreate -L+xG iscsi_lv_xx /dev/vg
    Remember that the NFS exports (files ystems) are going to be resized on the storage server itself (lvresize -L+xG nfs_lv /dev/vg; resize2fs /dev/vg/nfs_lv). But the iscsi LUNs are going to be resized on the initiator itself because that's where the FS got initialized. Be extra careful when manipulation partitions / LVs / VGs / PVs as it can cause data loss.

    Regards
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  4. #4
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    Thanks for the information that's very helpful. But will LVM effect performance I have read some comments around that LVM has some large performance overhead and as a result is slower. Is this true or a misconception or not even notable ?

  5. #5
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    Quote Originally Posted by ctnetadmin View Post
    Thanks for the information that's very helpful. But will LVM effect performance I have read some comments around that LVM has some large performance overhead and as a result is slower. Is this true or a misconception or not even notable ?
    I've only heard the contrary.
    Jacob Wall - GetCloak.com

  6. #6
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    Quote Originally Posted by ctnetadmin View Post
    But will LVM effect performance I have read some comments around that LVM has some large performance overhead and as a result is slower. Is this true or a misconception or not even notable ?
    There's obviously some slight performance hit. But the benefit of LVM is far greater than the negligible hit. Research a bit about LVM readahead and how it can improve read performance (ex: blockdev --getra /dev/vg/iscsi_lv_01 and blockdev --setra 2048 /dev/iscsi_lv_01. The blockdev tweaks are things that you can do as a last step to measure/improve performance.

    Regards
    UNIXy - Fully Managed Servers and Clusters - Established in 2006
    [ cPanel Varnish Nginx Plugin ] - Enhance LiteSpeed and Apache Performance
    www.unixy.net - Los Angeles | Houston | Atlanta | Rotterdam
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  7. #7
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    So for a setup with 3 or 4 VM's running off a storage server is it really worth utilizing iSCSI rather than just NFS, after all NFS provides ease of backup and after reading some benchmarks it appears software iSCSI vs NFS is pretty much equal.

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