[linux-lvm] LVM for a Database

Heinz J . Mauelshagen mauelshagen at sistina.com
Wed Nov 27 11:24:10 UTC 2002

On Tue, Nov 26, 2002 at 09:38:26PM +0100, Anders Widman wrote:
> > We are in the process of building a database on a 4 processor 1.8GHz, 4GB RAM Dell 6650.
> > I am trying to figure out the most efficient way to use LVM for our raw data storage.  We have a RAID array with 8x36GB drives in it.  Should I do a raid 1+0(mirror 4 disks, and span them to get
> > one logical volume)?
> This  is  a  fast  and easy setup.. But what will you use to the disks
> for?  RAID  5  is generally fast and space efficient, though it can be
> slower on writes.
> > If so this leaves me a /dev/sdb.  Or would I get better performance if I mirror 1 + 5, 2 + 6, 3 + 7, 4+ 8 to give me /dev/sd[b-e].
> > Is it possible to figure out where the center of our spindles are?  So I can arrange for the heads to spend little time seeking?
> By  mirroring  pairs  your would end up with 4 logical drives that you
> can  use LVM (with striping if necessary) on top and have more freedom
> to  replace and change drive setup (like if you want to replace a pair
> of disks for newer/bigger models).
> I am not sure if LVM 1.x support changing size of striped volumes, but
> LVM  2  should  have  much  freedom  to do basically whatever you want
> (still in beta though). Disk spanning with LVM 1 is quite fast though,
> for most applications.

LVM1 stripes are restricted to the physical volume.
LVM2 doesn't have that constraint.

Using LVM1 is in general a good idea for databases, because you can
relocate data later once you realize performance problems on certain
spindels with pvmove(8).

pvmove is the only missing major feature in LVM2 (to be added ASAP).
Smooth migration from LVM1 to LVM2 without loosing any VGs/LVs is possible.

Once pvmove is available on LVM2 that is the path to go.

> > Any perfomance hints would be greatly appreciated.
> > thanks
> > Joe K.
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/


Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***


Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
Mauelshagen at Sistina.com                           +49 2626 141200
                                                       FAX 924446

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