Rupert Heesom <[EMAIL PROTECTED]> writes:
> I seem to be having problems when configuring my disk setup during the
> net install for sarge amd64.
>
> I'm trying to configure /home to be an MD within an LVM container.
> Although the install can configure it, when I've rebooted the install,
> and installed evms, then it seems the LVM container has the wrong MD
> in it.
>
> Without going into further details, has anyone else tried to configure
> an MD within an LVM using the amd64 install?
I've setup raid on lvm before but not in D-I. There is one big problem
with it though. From what I understand when resyncing the raid the
raid I/O gets tunneled back through the I/O layer to do the device
mapper magic and thereby flags the disks as busy. Since raid
rebuilding only takes idle I/O it drops down to the minimum rebuilding
speed (default 1MB/s).
So if you want to use raid on lvm you have to increase the
/proc/sys/dev/raid/speed_limit_min to something that will finish
within reasonable time.
> I'm wondering about using EVMS to reconfigure the /home LVM container
> that was created at install.
>
> Also how do those using MD (raid1) handle the SWAP partition? Do you
> leave the 2 partitions that would be used for an MD seperate and use
> each one for swap space, or do you use an MD for swap space?
>
> Rupert
I have swap on raid1 now too, didn't used to bother.
The reasons are simple:
- If the swap fails the system fails pretty badly.
- Raid1 takes basically no cpu time, just doubles the I/O (DMA) to the
controler.
- Normaly you don't swap. Some unused pages get swapped out over time
but nothing in use normaly. Assuming you have enough ram that is.
- Swapping in is the same speed with raid1 as without while swapping
out hopefully only happens to long idle pages (see point above) and
doesn't block. Linux already swapps pages out if it feels they could
be used better as cache and not only when it needs too (and would
block).
- what is an extra 1GB for the swap raid1 compared to the total
diskspace
So you see, no real disadvantages and the big advantage to survive a
disk crash. The choice is easy.
MfG
Goswin
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