Hello John, Tony,
Thanks for your responses. I think I will try to go with John's approach
(ie via gmirror), as I've used it previously for a raiding on
equally-sized disks.
John, I will be trying out your suggestions in a while. Hope to get your
help later down the road. :)
Tony, I'm quite sure your trick will work. I'm just too noob on FBSD to
trick vinum. :P
John Nielsen wrote:
On Monday 11 December 2006 03:47, Foo JH wrote:
Hi all,
I unfortunately have 2 uneuqally sized SATA disks to set up a mirrored
shared folder: 80GB and 120GB. On the 120GB I plan to set up this way:
/temp 2GB (double the system memory)
/shared 80GB
/ 38GB
I plan to mirror /shared onto the 80GB. It won't be bootable, but I can
always mount it onto another FreeBSD machine.
I've read some articles on mirroring on non-equal disks, notably:
http://people.freebsd.org/~rse/mirror/
My question is: is there an easier way to do this? The example looks
quiet daunting for a noobie FreeBSD admin like me.
I would use gmirror. The example page you cite is very thorough and covers
multiple scenarios. I have found gmirror to be extremely easy to use and set
up; much more so than gvinum or even ataraid.
Gmirrror allows you to use any geom provider as a member (consumer) of a
mirrored set. That includes entire disks (e.g. ad4), slices (e.g. ad4s1),
partitions (e.g. ad4s1a), or even other complex structures (such as a gstripe
set).
The only hard part is going to be labeling the 120GB disk correctly. You will
most likely want to do it manually using bsdlabel. One approach would be
something like the following. Assume ad4 is the 120GB disk and ad6 is the
80GB disk. Boot up using a FreeBSD install disk and go into "Fixit" mode.
# fdisk -BI /dev/ad6
(it's safe to ignore the warning here)
# bsdlabel -Bw /dev/ad6s1
# sysctl kern.module_path="/dist/boot/kernel"
# gmirror load
# gmirror label -b load shared /dev/ad6s1a
("shared" is the name of your volume.. you can use whatever you want)
# gmirror list
(will show you details about your new "broken" mirror. Make a note of
the "Mediasize" number listed under the consumer.)
# fdisk -BI /dev/ad4
(it's safe to ignore the warning here)
# bsdlabel -Bw /dev/ad4s1
(these are only needed if you don't like/don't know how to use vi)
# EDITOR=ee
# export EDITOR
# bsdlabel -e /dev/ad4s1
Now comes the tricky part. The number shown on the c: line of the label is the
number of 512-byte sectors on the disk. It's good practice to leave 16
sectors unused at the beginning of the disk; you can see this in the default
whole-disk a: line. Figure out how big you need to make the slice for the
other side of the mirror by dividing the Mediasize number you noted
previously by 512. Then figure out how big you want your swap (if any--you
didn't mention any above) and /temp partitions by multiplying out to the
number of bytes then dividing by 512. Add all of that up plus the 16-sector
space at the beginning and subtract from the size (c: line) to determine how
much is left for /. Calculate all the offsets and put in the fstype (either
4.2BSD or swap), and put zeroes in the other columns.
As a reference, here is one of my disks:
# /dev/ad4s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 6291456 1048502 4.2BSD 0 0 0
b: 1048486 16 swap
c: 156312513 0 unused 0 0 # "raw" part, don't
edit
d: 117266625 39045888 4.2BSD 0 0 0
e: 31705930 7339958 4.2BSD 0 0 0
Save the label and exit the editor.
Now to finish up:
# gmirror insert shared /dev/ad4s1e
(be sure to use the actual partition device you set up above)
# newfs -U /dev/mirror/shared
( /shared )
# newfs -U /dev/ad4s1a
( / )
# newfs -U /dev/ad4s1d
( /temp )
Then exit fixit mode and do a Standard installation. Don't let sysinstall
re-label or newfs anything, just specify the mount points for your /
and /shared filesystems. You'll have to mount the mirror after you're done
with setup (just put it in /etc/fstab manually).
Obviously, you should understand what all of the above does before you do any
of it, and may need to make changes.
Good luck, and feel free to ask additional questions.
JN
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