using dmraid

bbbb · 12-23-2005, 08:46 PM

hi,

I just finished my first RAID story, and it had a happy ending after all. thanks to dmraid

. here's my specs:

motherboard: Asus P5GDC Deluxe
onboard controller: Intel ICH6R
HDD's: 2 * Maxtor 300 GB SATA
xtra hdd: some immediately supported pata
Mandriva 2006.0 official i586 free (netinstall)

so, first of all, I created two raid drives called chris and ted using the controller bios. I continued to install the os on the pata, the raid drives were NOT recognised during the install. I downloaded dmraid, did a shitload of research, and finally came to the conclusion that these were the steps to follow:

first: check if dmraid can find the raid drives you created. run

Code:

dmraid -s

you should see some satsifying output I suppose... I got this at first run:

Code:

[root@mreggsybit bb]# dmraid -s
*** Group superset isw_begabaiadd
--> Subset
name   : isw_begabaiadd_ted
size   : 209715200
stride : 256
type   : mirror
status : ok
subsets: 0
devs   : 2
spares : 0
--> Subset
name   : isw_begabaiadd_chris
size   : 376398848
stride : 256
type   : mirror
status : ok
subsets: 0
devs   : 2
spares : 0

which I thought was satisfying enough

.

second: you have to modprobe dm-mirror. now, I suppose that the "mirror" part is because of my raid 1, try fooling around with this if you get no output during step 3. for me, the command was:

Code:

/sbin/modprobe dm-mirror

third: you make dmraid just activate everything it can:

Code:

[root@mreggsybit ~]# dmraid -ay -v
INFO: Activating GROUP RAID set "isw_begabaiadd"

(note the "INFO: " output; if you didn't get it, you probably failed)

and it was here that I really wondered what to do next. I looked for a long (long!) time, but couldn't find anything. answer: there is nothing to be done; it is finished. I finally tried out this:

Code:

[root@mreggsybit ~]# updatedb
[root@mreggsybit ~]# locate chris
/dev/mapper/isw_begabaiadd_chris

and that's how I discovered that the raid partitions were neatly put in /dev/mapper/ . to make it a little easier to manage, I did

Code:

[root@mreggsybit mnt]# cd /dev/
[root@mreggsybit dev]# ln -s mapper/isw_begabaiadd_chris raid-chris
[root@mreggsybit dev]# ln -s mapper/isw_begabaiadd_ted raid-ted

and now, the only thing left was to mount them. not even specifying a type (I love automagic). result:

Code:

[root@mreggsybit mnt]# df
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda1             2,0G  243M  1,7G  13% /
/dev/hda7              67G  129M   66G   1% /home
/dev/hda6             2,9G  919M  1,9G  33% /usr
/dev/mapper/isw_begabaiadd_chris
                      177G  129M  168G   1% /mnt/chris
/dev/mapper/isw_begabaiadd_ted
                       99G  129M   94G   1% /mnt/ted

if you completed step 3 succesfully but really don't know where your device is now, retry step 1 to check if step 3 actually worked. you should see "--> Active Subset" now where there used to be "--> Subset" . if you don't, step 3 failed. recheck step 2.

I discovered step 2 by coincidence; in the very beginning I started harddrake to check if maybe the wizard would be able to do raid, and in the log messages I saw him run that command. After rebooting step 3 failed and after a while I figured out that it was that command that made the difference.

well, that was it for my little story of success

although it is of course very unsignificant, I know I would have loved to find at least ONE dmraid tutorial out there, and I hope that the next person who will have to do the same as me will have less trouble

. thank you, dmraid.

-b^4