[olug] The "other" raid utility usage

[Matthew G. Marsh]

OK - the posting on the software raid stuff done at the last meeting by
Adam got me wondering. Last time I played with SoftRaid was back in
2.1.{something} and it was ok but not amazing.

LSS - raidtools would not compile (no surprise there as it is a rathead
util) so I found one called mdadm.

http://www.cse.unsw.edu.au/~neilb/source/mdadm/

I am quite happy. This compiles static! and is only 854228 when compiled
static. Tested it without libraries and it worked fine.

It also will do everything the raidtools will plus it has a daemonized
monitor mode that sends email or gens SNMP traps for array messages...

Also found some scsi generic utils that enable spinup/spindown and a whole
lot of other neat things (I run pretty much only SCSI on my servers) and
so I figured maybe I would post what I played with FYI.

SG3 - http://www.torque.net/sg/u_index.html  (sg3_utils-1.03.tgz)

First off - array = (10) 18.3G UW drives in a hardware rack (IBM EXP15)

Using a SymBios UW controller (happened to have handy on the Compaq server
and it was not even in use...)

1. Created partitions (not needed actually - see docs on mdadm)
	1.1 (1) per drive - full size
2. Created RAID5 array
	mdadm --create /dev/md0 --level=5 --raid-devices=10 /dev/sd[a-j]1
3. Formatted as ext3
	mke2fs -b 1024 -j -v -L "DATA" /dev/md0
4. Mounted array
	mount /dev/md0 /data

Then decided to play with the system to see how to recover the array on
failure (thanks paul...)

Pulled out a drive.
OK - degraded array.
Put back in the drive.
Hmmm - no nothing happened.
fdisk the drive - no such device - whoops.
went and found sg3 utils
used them to spin up drive  sg_start /dev/sg2 1
fdisk works fine - partition still exists
now used mdadm to fail, remove, and add back in drive
	mdadm /dev/md0 -f /dev/sdc1 -r /dev/sdc1 -a /dev/sdc1
Adn the array starts to rebuild.

Cool!

HTH.

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Matthew G. Marsh,  President
Paktronix Systems LLC
1506 North 59th Street
Omaha  NE  68104
Phone: (402) 553-2288
Email: mgm at midwestlinux.com
WWW:  http://www.midwestlinux.com
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