[CentOS] Seeking pointers to info about LVM migration and performance

Fri Jul 6 23:05:41 UTC 2007
John R Pierce <pierce at hogranch.com>

Bart Schaefer wrote:
> We have a large MySQL database currently running on a CentOS 3.x
> server with an external SCSI RAID device.  This is currently an ext2
> filesystem because it was migrated once previously from an even older
> RedHat system.

umount /dev/sdb1
tunefs -j /dev/sdb1
vi /etc/fstab    (and, change ext2 to ext3 on the mount line for this 
mount /dev/sdb1

and voila, its EXT3 now, with journalling.

> We need to add storage capacity to this database and
> prepare for additional future growth.  One of the options under
> consideration is to move to CentOS 5 and use LVM.
> Of some concern is that we run some pretty heavy-duty queries against
> this database in close to real time, so we don't want the switch to
> scalable storage to have a significant impact on read latency.
> Consequently I'm looking for sources of information on two topics:
> - What kind of performance can we expect from an LVM group as compared
> to mounting the RAID array directly?
> - What's involved in migrating our filesystem from ext2 to LVM with a
> minimum of downtime?
> Thanks in advance for directions.
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