Smoke and Mirrors: mirrored concat / concat mirrors

Smoke and Mirrors: mirrored concat / concat mirrors

Post by Sam » Tue, 20 Jun 2006 20:53:03


Hi all - I have a JBOD with a bunch of disks, and need to create a
~200gb slice on this using LVM on Sol 9. I've allocated 2 disks to a hot
spare pool already. This leaves me with 6 new disks in order to create
my ~200gb slice. They're all on the same controller, nice (not my choice).

I'm thinking of ways to do this.


Example 1:

mirror d4, made up of a concat of disks 0,1,2 (d14) and a concat of
disks 3,4,5 (d24)



d4

d14 d24
0 1 2 3 4 5

If I lose a disk on one side the spare should kick in, but if I lose
another disk on the other side whilst this is syncing, I've lost my
data. I could lose up to three disks (on one side only) and still serve
up data.

Example 2:

mirror d4, made up of a concat of mirrors d14 (disks 0,1), d24 (disks
2,3) d34 (disks 4,5)

d4

d14 0 1
d24 2 3
d34 4 5

Here I can lose up to 3 disks (in different mirrors) but if I lose 2
disks in the same mirror I'm knackered. However if I lose one disk I'm
only syncing up 72gb of data as opposed to ~200gb in example 1.

Is example 2 any better than example 1 for resiliency? Will LVM even
allow me to do this? If anyone has any suggestions I'd be most
appreciative. Resiliency is more important than outright speed, and read
speed is more important than write speed.

Maybe I should stick with example 1.

Or is it too early on Monday and I haven't had enough coffee yet :) Damn
long weekends and no sleep.

cheers

Sam
 
 
 

Smoke and Mirrors: mirrored concat / concat mirrors

Post by ptribbl » Tue, 20 Jun 2006 21:23:25

In article <zewlg.48082$ XXXX@XXXXX.COM >,
Sam N < XXXX@XXXXX.COM > writes:

This is the correct way to do it.

You will only lose data if you lose the matching disk on the other side.


You can't do that with disksuite, and there's no need as the
implementation gives you the same benefits as your first case.

--
-Peter Tribble
L.I.S., University of Hertfordshire - http://www.yqcomputer.com/
http://www.yqcomputer.com/ ://ptribble.blogspot.com/

 
 
 

Smoke and Mirrors: mirrored concat / concat mirrors

Post by Sam » Tue, 20 Jun 2006 22:27:52


Yup, after I woke up a bit I did 1 :)

cheers

Sam