[nSLUG] RAID and partitioning

Daniel Morrison draker at gmail.com
Sun May 6 16:08:20 ADT 2007

On 06/05/07, Bill Davidson <billdavidson at eastlink.ca> wrote:

"partionable array", so what do you know, it is possible :)
Very cool.

> So...  I have (or my daughter's school has) this box with 5 identical
> 36GB ultra-160 SCSI drives.  The on-board Adaptec AIC-7899 controller
> has two channels, so I put three drives on one channel and two on the
> other.

Unlike with IDE, there's not much reason to spread the drives out over the
two controllers (unless you have physical limitations, like not having a
big enough cable for them all).  The controller should be able to operate
them all at full speed on the same chain.  If you later add a slow device
(e.g. tape drive or cdrom) which cannot operate at Ultra 160, then the
drives on the same controller as that device may have to operate more
slowly.  So it might make sense to put all the drives on one controller
and save the other one for non-disk devices.  Just my 2 cents spur-of-the
moments thoughts.  Since Linux raid writes metadata in the superblock of
each device, you can always rearrange the disks later anyway you want, and
everything will still work.

> I'm thinking I'll create two partitions on each drive, one small
> one (say 128MB) and one large one.  I'll use the small partitions on sda
> (id 0 on channel A) and sdd (id 0 on channel B) as a RAID1 array to
> mount at /boot.  I'll use the other three small partitions for swap.
> Then I'll use all five large partitions for a RAID5 array and create
> logical volumes on that for everything else.

Sounds good.  I noticed you put a mirror of /boot across two controllers,
which means you could boot even if one of the two controllers dies.
However since the raid 5 is spread across two controllers, you wouldn't
have an OS to boot into anyway.  So although having a mirror for /boot is
a good idea, it probably doesn't matter which two disks you put it on.

Another alternative would be to use raid 1 for all of /, /boot, /usr and
whatever else your OS needs, and then put only user data on the raid 5.
Then you could boot up even if a controller dies.  Probably not worth it

> Now I just have to pick a distro...

Slackware! :)

> Oh, and does anybody have a line on a Voltage Regulator Module for a
> Dell Poweredge 1400SC?

Not personally.  Maybe this would do?



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