[ale] EVMS + software RAID??

[Jeffrey B. Layton]

trey wrote:

>Has anyone had any experience with this combo? I know that I did a
>similar thing a year or two ago with a Solaris 8 system using their
>Disksuite. It was like, create stripes, then create metadevices, then
>create cats?? Something like that. I guess the long and short of it is
>that I want to mirror two 120gig drives. Partition table is like:
>root - 5000 meg
>swap - 2000 meg
>
>The remaining 113gig or so I want to be able to create metadevices and
>have some flexibility in resizing them dynamically as needed, without
>making my mirror desync.
>I guess the question is multi-part.
>
>1 - Does anyone have any experience with EVMS? Any caveats?
>2 - Do I want to create one big 113 gig filesystem, convert it to a
>metadevice, then mirror that metadevice, then subdivide that
>metadevice into "partitions" ? Or have I mucked up the order of
>operations here?
>

   Let's see... I'm not sure I follow what you want to do. You've got two
120 gig drives with 5 Gigs for root and 2 gigs for swap on each.
Is this correct so far? Do you want to mirror root? (It doesn't make
much sense to mirror swap, but you can strip swap across the
two drives). So, do you want to mirror the first partition (/dev/hda1)
on each which contains root (RAID-1)? Then /dev/hda2 is used for
swap on each drive (I'll have to look at around at how you setup
striping for swap).
  Then with the remaining about 113 Gigs you want to mirror them,
but have the ability to grow? If so, you can use software RAID-1
to mirror the partitions (for the sake of argument /dev/hda3) and
then build a logical volume on top of this mirror. Or you do the
opposite, build a LV on each drive, then use software RAID-1
to mirror them. I don't know which one would be better or why.
   Of course, you can carve up the 113 Gigs as you want and mix
and match software RAID and LVM.
   On the topic of EVMS, I have used it in the past. I really liked it.
However, if you have followed the 2.5 kernel development, EVMS
is toast except for the user portion of the code. EVMS will be built
on top of the Device Manager (DM) and it appears that LVM2 will
be put into the 2.5 kernel RSN. I use LVM at work and it's just fine
(it's very similiar to the HP LVM). I had only one problem when a
disk in the LVM died (one of the PV's). EVMS allowed me to
mount the LV as read-only and pull whatever data I could off of the
LV.
   If you need to read more about LVM go to www.sistina.com and
look for LVM. To learn more about software RAID, I recommend
the following articles:

http://www-106.ibm.com/developerworks/linux/library/l-raid1/index.html
http://www-106.ibm.com/developerworks/linux/library/l-raid2/?dwzone=linux

Good Luck!

Jeff





>
>-- Trey
>+++--------------------------------------------------------------+++
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>Trey Darley - Chief Technical Monkey
>AIS Computers - www.aiscomputers.com
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>[Please note that the opinions I express are not to be in any way
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