topic Re: RAID 1+0 question in Disk Enclosures

RAID 1+0 question

Wautier — Fri, 17 Oct 2003 08:49:44 GMT

Hello,
I want to buy a server with 2 scsi disks of 36gb.

I want to create a volume that would be 6GB to put the system into it.

Then i want to use the rest 2*30 Gb to create a raid 0 (striping) to have a fast access to my data (It would contain a database).
I will have also to buy a DLT to have a backup of my data.

What do you think of this solution? It's cheap, fast for my data, but i do not know if it will work.
TIA for your answers
Dirk

Re: RAID 1+0 question

Leif Halvarsson_2 — Fri, 17 Oct 2003 09:13:58 GMT

Hi,
Are you going to use software RAID or a hardware RAID controller.

With only two disk you use RAID 1 (mirroring), RAID 1 + 0 needs 4 disks or more.

The most common solution is to mirror the physical drives and then partition it in 1 or more volumes, either in the controller (LUNS = the os see this LUNS as separate physical disks) or in the OS.

It is very easy to test if it works, remove one of the disks when the system is up.

Re: RAID 1+0 question

Wautier — Fri, 17 Oct 2003 09:44:45 GMT

OK thanks for the answer.

I want to use hardware raid.
I want to have a part of my 2 hard disks in raid 1 and the rest on my hard disks in raid 0.
I know that raid 1+0 needs 4 disks.

Dirk

Re: RAID 1+0 question

Leif Halvarsson_2 — Fri, 17 Oct 2003 11:29:40 GMT

Hi,
Most (all ?) entry-level RAID controllers don't support a such configuration. Each physical disk can only belong to one RAID set and each RAID set can only work at one RAID-level. With two disk you can choose RAID 0 (striping = fast and more space but no redundancy) or RAID 1 (mirroring = vaste half the capacity but with redundancy).

More adwanced (and expensive) controllers (for example the EVA arrays) work in a different way (block-level RAID) where one physical disk can store data in more then one RAID level.

Re: RAID 1+0 question

Ronald Hendriks — Mon, 27 Oct 2003 15:40:58 GMT

A simple smart array controller can do this.

Build an array and then create logical drives from it. This can be a RAID 1+0 and a RAID0 or a RAID5 set

RAID1 doesnt exsist on a smart array, a 2 disk array can have a RAID 1+0 logical drive (which is a striped mirror set with one stripe)

I would think again about using RAID0 for a database....