Re: Hot adding active disk to RAID1?

Thus spake Peter Sj?berg (peters@techwiz.ca):

On Sat, 2004-02-07 at 12:37, Mike Perry wrote:

quoted

Thus spake Mike Perry (mikepery@fscked.org):
Anyways, sorry for the spam, but I imagine at least one other poor sap
out there will find this useful ;)

I'm that one.
I ended up at the same place but for another reason. I was in a hurry to
build my system and knew that converting a ext3 to raid would cause some
problem because of some extra raid info, so I defined a raid1 with only
one disk. Later I bought the other disk and tried to add it by changing
/etc/raidtab but that did of course not work and it was at this point I
started to actually read the doc...

Yeah, this sounds like my exact scenario, give or take a few details.

I saw reference to an old version of mkraid that would reinitialize the
superblock only (--superblock-only) and keep the data, but newer
raidtools doesn't do that. If that been there or some manpage in the
later version describing it a bit clearer I could dear to do mkraid -f
but with all incarnations of the raid software I no longer know what is
safe in my version

I concur. The manpages really should clear up that raidhotadd (and mdadm
-a) only add spares. And they should further clarify that spares are
essentially useless and lie dormant.. The names of these
commands/options are very deceptive to the new user...

My current state is that I have root mounted as /dev/md0 created with
one disk (/dev/hda5) as disk 0. I have since then added another disk and
partitioned it equal. I now want to add /dev/hdc5 to md0 (was never
mentioned before). If I add that to raidtab as failed-disk and do
"mkraid -f", will I loose anything?

I would put your data on both just in case. But yes, this should work
just fine. The sync should start as soon as you raidhotadd a failed
disk.


Sorry for the late reply.. Was away for the weekend (which was the cause
of my original impatience and need to quickly find a solution..) 

-- 
Mike Perry
Mad Computer Scientist
fscked.org evil labs