Hardware RAID 5 on PE 4600 and linux LVM

jason andrade jason at dstc.edu.au
Sun Nov 10 05:14:01 CST 2002


On Sun, 10 Nov 2002, Dario Palmisano wrote:

> Hello,
>
> I am going to buy a PE 4600 with 4 x 73 Gb disk in RAID 5 configuration (using
> the hardware support of the PERC 3/Di controller).
> I would like to know if it is possible to add other disks to the RAID 5 volume
> without distrupting the previous content of the volume?
> In case it is possible I wonder if the linux LVM (not used for RAID but just
> for logical volume management) automatically recognize the augmented size of the
> volume or maybe I need to execute some procedure?

Hi Dario,

I highly recommend you read the LVM howto, e.g

http://ldp.planetmirror.com/HOWTO/LVM-HOWTO.html


increasing the size of a volume requires you to both add extents under LVM
but also at the filesystem layer - ext2/3 is not "auto extending".  i cannot
comment in detail about the other filesystems (e.g xfs, reiserfs) but i think
you can also extend them.  the short version of your answer is "yes", you
can add additional disk space later to grow the filesystem, possible without
even needing to take the filesystem offline.

please consider how you are going to do this though.  were you planning on
simply adding more disks to the RAID5 volume and somehow growing that (can
someone else comment on whether this is destructive or not?) or were you
going to add another 4*73G in a second raid5 array later ?

be aware that from reports form people i've had, LVM1 performance can be
significantly lower than using a direct disk.  LVM2 is meant to have cleaned up
a number of things and has substantially better performance, when it is released.


regards,

-jason




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