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Brisbane Mango
Asked: 2009-09-19 03:08:40 +0800 CST

How to extend a SAN-based Vdisk in Red Hat without rebooting?

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First of all, I'm quite new to Linux so forgive me if I use the terms 'disks', 'partitions' and 'devices' incorrectly below!

I have a Red Hat 5.2 x86_64 server with kernel version 2.6.18-92.el5. I have several SAN-based Vdisks presented to the server, appearing as /dev/sdx and, when I create a partition, /dev/sd*x*1 . The SAN is an hp EVA-8100.

Occasionally I need to extend a disk. I can increase the size of the Vdisk via the hp Command View EVA software, but the only way currently I can get the server to recognise the additional space is to reboot the server.

For various reasons I'm not currently using an LVM. Is there a command or method I can use to get the server to recognise the additional space without rebooting the server?

Many thanks,

/Neil

linux

3 Answers

  1. This is what I have used for systems with dm-multipath and LVM; modify as needed:

    1) Increase size of LUN in SAN
2) Check with "multipath -ll" which devices belong to said LUN
3) For each device above, do "echo 1 > /sys/block/sdX/device/rescan"
4) Go to multipath command line with "multipathd -k"
5) For each device, do "del path sdX", "add path sdX" while hoping that
the multipathing functionality works as advertised and fails over properly.
6) "resize map multipath-map-name"
7) Exit multipath command line (Ctrl-D), check with "multipath -ll" that
new size is seen.
8) pvresize, lvextend, resize2fs
9) Profit!

    This works as of RHEL 5.3.

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  2. /* THIS MAY RESULT IN DATA LOSS */

    Here's how to do it without LVM

    1) Resize the LUN on your SAN

    2) Unmount the partition

    3) fsck the partition to reorder the data to the beginning

    4) Here's the scary part, fire up fdisk and delete the partition making note of it's starting block

    5) Re-create the partition with the same starting block but with the new end block

    6) Run resize2fs (assuming your running ext2/3)

    7) Remount your resized partition

    8) Profit

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