How do I know if my RAID is working?

rtaft · 07-20-2006, 08:24 AM

I set up a RAID device when I installed FC5. I think I set up sdb1 as either a mirrored or redundant RAID but I don't know if it is actually working. I can't mount /dev/sdb1, it says its already mounted but /dev/sdb* is not listed in /etc/mtab.

I basically need to know if I set it up right and if its working, otherwise I need to get it working.

acid_kewpie · 07-20-2006, 08:37 AM

if you mean software raid then check the output of "cat /proc/mdstat"

rtaft · 07-20-2006, 08:46 AM

it just says:

Personalities :
unused devices: <none>

acid_kewpie · 07-20-2006, 08:53 AM

that'd suggest you've no raid setup at all then. normally it's very user friendly, showing all devices in each md object etc...

Code:

Personalities : [raid5]
md0 : active raid5 hdg1[2] hde1[1]
      320159104 blocks level 5, 32k chunk, algorithm 2 [3/2] [_UU]

unused devices: <none>

here i have /dev/md0 made of two devices out of three, one failed disk.

rtaft · 07-20-2006, 08:57 AM

Thanks, I think I'm heading in the right direction now. I was using webmin to try to see if it was set up, but the only thing it ever lists in the RAID section is sdb2 as both source and destination. I found some docs on it, I'll keep looking into how to set it up.

acid_kewpie · 07-20-2006, 09:04 AM

well if it's software raid then you would ned up with a device like /dev/md0 not /dev/sdb2 or something. if it was a pure hardware raid solution then linux would see /dev/sdb2 or whatever still as it wouldn't know about the raid.

rtaft · 07-20-2006, 09:30 AM

I tried to set one up, but things aren't as easy as these docs make them sound.

I used:
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda3 /dev/sdb2

where sda3 is the /var partition and sdb2 is a raid partition.
I get an error that sdb3 is busy. I could unmount it and try it, but I don't want to hose any current work that is on it. I'd really like to take all of sda and mirror it to sdb, they are both the same size, instead of doing individual partitions.

Am I even close to heading in the right direction? I worry that maybe sda isn't set up right and I can't do it now that there is data on it or something like that.

acid_kewpie · 07-20-2006, 04:26 PM

no no, not close. if you convert something to raid you WILL lose all the data! i would possibly suggest just running a cron job or similar to copy all files from the main drive to the secondary one.