Gordon Henderson wrote:
[]
Heres a scenario that I use myself. Firstly I'm not a fan of a separate
/boot partition - thats all to do with me being a boring old fart and new
hardware not needing it... So..
If you partition all 4 disks identically it'll save you headaches later
when you need to replace one.
So I'd do it like this:
6 partitions: The first used as root, 2nd as swap, 3rd as /usr, 4th as
/var 5th as your data and 6th as the backup for the data. You can combine
root and /var and even /usr if you like to make it simpler. There are pros
and cons for each way. (as well as holy wars)
Combine the root partitions together with RAID1 and 2 hot-spares. All
others in RAID5. (including swap, yes, I know, not efficient, but if you
are swapping heavilly you are runing sub-optimally in the first place -
buy more memory!)
That's excellent advise. Here's some more suggestions.
o if you use identical disks, number your mdN devices after the partition
number (md1 on sd[abcd]1, md5 on sd[abcd]5 etc) - this makes life a
bit easier, and in particular makes hot-adding of new disk easier:
for i in 1 2 3 5 6 7 8 ...; do
mdadm --add /dev/md$i /dev/sdd$i
done
o instead of raid5, use raid1+0 for swap. That is, create two raid1
arrays - md20 on sd[ac]2 and md21 on sd[bd]2, and list both
md20 and md21 as swap devices in fstab.
o keep your root filesystem on the first partition on every disk,
without spares, i.e. build raid1 array out of all 4 disks. It
is ok to have very small root partition, e.g 256Mb should be
sufficient (provided /usr and the rest are separate partitions).
This way, you will be able to boot of any disk (with or without
md1 running), and you will have sufficient tools to recover after
any problem. Ofcourse, /boot will be keept in /.
So, the "final layout" (I use it on many my systems) looks like:
md1 raid1 on sd[abcd]1 root 256Mb (active partition)
md20 raid1 on sd[ac]2 swap
md21 raid1 on sd[bd]2 swap
md3 raid5 on sd[abcd]3 /usr
md5 raid5 on sd[abcd]5 /var
md6 raid5 on sd[abcd]6 /home
...
or something like that:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/md1 124323 86893 31011 74% /
/dev/md2 4434560 1867950 2341318 45% /usr
/dev/md5 2205258 793952 1299274 38% /var
/dev/md6 8845860 4512008 3884458 54% /home
...
/mjt
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