RAID10 setup

[Phil Lewis]

This question was asked a few weeks ago, but the original poster
must have had their questions amswered. As follow-ups offered
further assistance given more detail, I wonder if I could be so bold
as to provide that detail for my own circumstances.

I have six disks:

ad4  - 500MB
ad5  - 500MB
ad6  - 500MB
ad7  - 400MB
ad8  - 500MB
ad10 - 500MB

These are SATA drives, with ad8 and ad10 on a PCIe SATA controller.

ad7 was my first disk and currently contains FreeBSD7.2-RELEASE.
I've been using that to gain some familiarity with FreeBSD, but it
need not be preserved (in fact, I'd rather not preserve it!). When I
built the machine, I just plugged the 400GB drive in any old slot,
so it can move if that makes sense. When I got the new drives I tried
to get identical to the 400GB drive, but couldn't. The 400GB drive
currently has a single slice using the full drive.

What I'd like to end up with is a three-way stripe across three
two-way mirrors, containing as much of the system as possible.

I understand that you can't boot from a stripe, so some part of some
disk will have to be outside the stripe. However, as the stripe will
also be limited to the smallest disk, I'm going to have 5 x 100 GB
bits left over anyway, so I guess /boot can go on one of these..?

If possible, I'd like set this up pre-install. If it has to be done
post-install, or is easier to describe how to do post-install, then
that's fine.

>From here on in, this email becomes speculative.

All of the examples I've seen for setting up GEOM stripes and mirrors
have used the raw disk as the base-level provider. On the other hand,
I've seen nothing that says that the bottom level cannot be a slice,
rather than a raw disk, and given the way GEOM works, I suspect this
is true.

My current plan, based on this assumption, is as follows:

With my current FreeBSD installation, create 2 slices on each 500GB
disk, 1 x ~400GB,  1 x ~100GB (the same size as the slice of my 400GB
disk, and the rest of the disk).

Boot from the FreeBSD 7.2-RELEASE dvd, and enter fixit mode. I'm
not sure which would be best, or even if both are feasible for what I
want to do. (I was at this point in my researchwhen I found this
post!).

>From here, kldload geom_stripe and kldload geom_mirror.

Then, create the three mirrors:

gmirror label -v main0 /dev/ad4s1 /dev/ad5s1
gmirror label -v main1 /dev/ad6s1 /dev/ad571
gmirror label -v main2 /dev/ad8s1 /dev/ad10s1

This should give me /mirror/main0|main1|main2, right?

Next create the stripe:

gstripe label -v -s 131072 raid10 /dev/mirror/main0
			/dev/mirror/main1
			/dev/mirror/main2
	(that's all one line)
	
	
If I'm right so far, then hopefully I should be able to boot to the
install dvd again (or just rerun sysnstall?), and from there I should
be able to choose a slice from outside 'raid10' to mount /boot, and
use 'raid10' for everything else. Do I need anything else on a
non-striped slice?

Maybe I could even create another mirror:

gmirror label -v boot /dev/ad4s2 /dev/ad5s2

and use that to mount /boot, leaving me with s2 on ad6,8 and 10 as
3 spare 100GB slices?

Or am I just way off track?

PS. I can't believe I'm talking about 300 'spare' GB! My first disk
was 20MB! And I never filed that!

All guidance much appreciated.

Phil

On 30 July, 15:03, John Nielsen <li... at jnielsen.net> wrote:
> On Wednesday 29 July 2009 15:54:42 Richard Fairbanks wrote:
>
> > OK, so this is what I want to do. I have 4 big fast drives that I want to
> > run inRAID10 (1+0). So, I'll need to mirror two sets of two disks, then
...
> > Of course, if there is a way to create the stripedsetoff mirrors before
> > installation then installing onto that stripe, that'd be perfect. I don't
> > know if that can be done. I'm sure someone has configured aRAID10
> > "standalone" system before. (Oh, I'm using 7.2). I'm just stuck at this
> > point!
>
> You need to consider where/how you are going to boot the system. It's
> straightforward to boot from a gmirror'ed UFS filesystem (the BIOS just uses
> one disk and thinks everything is normal), but you can't do the same from a
> stripe. You will either need a separate disk/device for your / or /boot
> partition or you will need to use slices/partitions on your disks. I
> frequently have the root filesystem on a small gmirror (partitions on 2
> disks) then use the equivalent "extra" space on the remaining disk(s) for
> swap.
>
> Youi should be able to do this pre-installfrom the Fixit shell. Boot to the
> live CD, enter the shell, kldload geom_mirror and geom_stripe, create the
> mirrors, create the stripe, exit the shell, start theinstall, and tell
> sysinstall to use the device node under /dev/stripe for your filesystem.
>
> Alternatively you could just do a regularinstallto one of the disks and do
> everything post-install. In this case you'd still create two mirrors but one
> of them would only contain a single disk at first. Then create your stripe,
> dump/restore your files, update fstab (in both locations if needed), reboot
> using the stripe, then add the original system disk into its mirror.
>
> If you provide more details of how you want your setup to look I can give you
> a specific walkthrough if needed.
>
> JN
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