need recommendations disk layout

[John Henrikson]

Hello folks,
I've just got a new L3000 machine with 2 18Gig internal drives and a RAID 4Si scsi controller connected to 4 18gig drives in a surestore disk system.
I'd like to get some opinions on the best way to set up these drives.. Our first thought is to mirror the 2 internal drives then set up RAID on the 4 drives connected to the raid card. Does that make sense to do?
thanks alot for your help.

[harry d brown jr]

John,

That's a very good plan. The internal disks would be for vg00, and the raid device would have it's own vg's.

live free or die
harry

[Rodney Hills]

Mirroring is good, but I would reserve it for operating system and production database. Mirroring does incur extra overhead in writing (although it does improve reading).

A lot depends on the amount of "critical" data will be placed on this system.

My 2 cents

-- Rod Hills

[Sanjay_6]

Hi John,

Looks good to me.

Hope this helps.

Regds

[Arockia Jegan]

That's a good plan.

[Helen French]

Well, it all depends on your requirement. Here are some thoughts:

1) Mirroring the root disk (internal normally) is a secure step. I would say it's almost obvious.

2) The RAID level for the external LUNs depends on you. If you want more speed (performance, access) RAID-1 will be better (hardware mirror). But here the available space will be only 50%. The RAID-5 will be my choice here, as it gives full redundancy and more space.

3) Before install the OS, plan the file system spaces, VGs and LVs.

[S.K. Chan]

Your plan is good, just want to add one point, when you carve up the 18GB as your root VG (vg00) don't use up all of its extents, leave some room for future expansion of the logical volumes.

[PIYUSH D. PATEL]

Hi,

Your plans looks good. May be you can mirror the internal disks using Mirrox UX and create a mirror for root disk also.

The other disks can be configured in RAID 5 according to your requirement.

Piyush

[Paula J Frazer-Campbell]

John

I back up what has already been said - yes mirror internal for OS remember to give lvols room to grow.

Depending what you intend to store on the other disk and its use depends on how best to configure them.

Lots of Reads ?
Lots of Writes ?
Critical data ?


Paula

[John Henrikson]

The main use of the system is for transaction processing..
thanks for the encouragement!

[John Henrikson]

Piyush-
do you mean that I should not only have a mirror of the os on the internal drive, but also create one on the raid drives?
thanks.. raid's new to me )

[Martin Johnson]

Remember, if you are going to mirror the OS, make sure the mirror is bootable.


Marty

[Tim D Fulford]

When you say RAID what type of RAID do you mean? I'm not familiar with RAID 4Si controller functionality, but I do know about AutoRAID & fc60 disk subsystems...

RAID 1 (Mirroring) [max space 36GB]
RAID 1+0 (Mirroring + stripes) [max space 36GB]
RAID 5 (Striping with parity) [max space 54GB]
RAID 1 - No massive performance hits. You can either do this using LVM or (I assume) using the RAID 4Si controller

RAID 1+0 - Is the best performing for reads & writes, but you will need to decide on the stripe size. As you can only have two LUNS in the stripe it will not make a great deal of difference ( we use 24 disks or 12 LUNS so you get a speed up of x12). I'm assuming the RAID 4Si card can do mirroring so you could use LVM to do the striping. OR you could ge LVM to do the whole lot, but the stripe size will be 4MB which is the PE size.

RAID 5 - This is great if you want to maximise your space, but random small writes performance will be poor. Reads will be good. Large writes will be good. Your RAID 4Si controller will need to do the RAID 5 stuff.

From what you have said I think you only have one controller so for best performance it is probably better to get the RAID 4Si controller to do the mirroring/RAID 5.

Tim