Re: lvm mirror or mdadm mirror or raid 5
On Sat, Sep 01, 2007 at 12:16:00PM +1000, Alex Samad wrote:
> raid 1 /
> raid 1 /boot
> raid 5 - pv
>
> I have been looking at why not to raid 5 and I would go to raid 10 but I can
> only put 3 drives in my machine.
>
> Currently have 3x250G and am looking at getting 3x500G, if I go to mdadm raid1,
> then I have 500G safe 500G unsafe which is not really what I want.
>
> I am going to stick with the /, /boot raid1 sets.
>
> But I was thinking about setting up the rest of the space as pv's and them
> using lvm's dm-mirror to manage the mirroring of space ? then if I don't want
> any redundancy on my space I can lvcreate without dm-mirror.
>
> Any one doing this, I haven't had much experience with dm-mirror.
> my thoughts were
>
> 1 big vgroup
> and lots of lv's some with mirrors and some without ?
I don't see a mirror option in Etch's LV create.
Here's how I would do it:
Partition 1: 3-way raid1 64 MB for /boot
Partition 2: 3-way raid1 300 MB for /
Partition 3: 1/2 of remainder on each drive
Partition 4: the other 1/2 of remainder.
Drives are a,b, and c.
md0: a1, b1, c1 >> raid1 /boot
md1: a2, b2, c2 >> raid1 /
md2: a3, b4 >> raid1, as PV for LVM
md3: b3, c4 >> raid1, as PV for LVM
md4: c1, a4 >> raid1, as PV for LVM
This way, you can still loose one drive and be safe. It gives you 750
GB safe, 0 unsafe.
Of course, performance won't be as good as if you had 4 drives so that
you didn't have more than one busy md per drive, but this is a good
compromise.
Why is it that you can't fit in a 4th drive? Are there only 3 bays?
What about an external bay that operates at SATA speeds; look at
addonics.
Doug.
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