Re: raidhotadd and RAID1

[Alvin Oga <aoga@Maggie.Linux-Consulting.com>]

hi ya michael

-- looks like we have a mis-communication.. lets try it again

my understanding so far..

- you had sda and sdb running as raid1 ( mirroring ) before 
	- if this not the case... all bets are off

- than sdb dies .... you replaced it ...

and now we are trying to rebuild the raid1 as it should be
( that the system can boot off either sda or sdb
	- simply doing something like  "hotswapadd /dev/sdb" 
	will automatically do all the magic to rebuild the raid
	as it was before the disk crashed

---------

now for more stuff...
	- if you replace a dead sdb with a new disk...
	and if you have raid1 properly configured...
	-- the system will resync and copy all the files
	for yoou ...automatically... need to do the hotswap command tho

	- you can watch its progress w/ "cat /proc/mdstat"
	and it will tell you how far along it is for
	resyncing the new disk into the raid setup

	- if you are typing/copying stuff manually...
	you do NOT have raid1 properly configured
	( and risk losing the remaining raid disk too )

- if during the time you only have 1 disk running, you
  are in degraded raid mode... and if you lose that remaining partition or
  disk and you lose everything...
	- bad idea to run in degraded mode

- hope you have daily backups (elsewhere)of the data on the raid subsystem

have fun
alvin


On Sat, 31 Aug 2002 tempsch@telia.com wrote:

> On 30 Aug, Alvin Oga wrote:
> > 
> > hi ya michael
> > 
> > if your system was not previously running as /dev/md0 ...
> > you do NOT have "raid up and booting and adding the second disk"
> > 
> > there is no such thing as "raid" on one disk..
> > ( well, within normal assumptions anyway ...
> 
> Oops, forgot to add CC to the list in my reply to you.
> 
> Short for the list:
> 
> The system *is* up and running on RAID1 (/dev/md0 as /) but with the
> second disk still failed (created the RAID with a failed disk directive
> in /etc/raidtab for that drive, then copied system to temp. mounted
> md0and did the necessary changes to have the system boot from RAID).
> The original drive (the one marked as failed when creating the RAID) has
> been nuked and repartitioned/reformatted.
> 
> The only problem is that raidhotadd considers the second disk to small.
> They're identical 18G IBM drives and partitoned identically - as far as
> fdisk can tell. I've tried increasing the size of the partition that's
> involved in the RAID1 at the cost of the swap partition, but still no go
> despite the partition on the disk I try to add is definately larger than
> the existing one in the RAID...
>