software RAID 1 mirror details?

[Alexander Dalloz]

Am Do, den 20.05.2004 schrieb Jack Howarth um 15:41:

>     I have some questions regarding the proper way to 
> set up a software RAID 1 mirror under Fedora on two
> identical SATA drives using the installation tools.
> In particular I am seeking to create a complete
> RAID 1 mirror so that if the main drive fails I can
> simply move it out and reboot under the mirror.
> What I am unclear on is how should I partition the
> two drives and how these partitions are related
> in the software RAID 1 mirror.

http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/install-guide/s1-diskpartitioning.html

Just create first the software RAID partitions you like with the size
you prefer, as just a rough example /boot = 100MB on sda and sdb, / =
4GB an both drives and swap = 512MB on both drives. Then in a second
step create the RAID1 arrays from both drive's partitions. From my
example choose the partitions you made for /boot on sda and sdb and set
them as RAID1 array. Do that with the others too.

>     My first inclination is to use DiskDruid in the
> installer to create identical sized partitions on
> both SATA drives (three partitions each...
> /boot, / and /swap). Of these I would only place the
> partitions for /boot and / in the RAID. My rational
> for this is that there is no point in mirroring the
> /swap partition. 

If you really want to have swap as RAID1 mirror too, that is possible
through Disk Druid.

>     Assuming this approach is correct, I am still 
> unclear on how the software RAID 1 mirror knows
> which partitions on each drive to map to each other?

The information is stored creating the RAID arrays. A map is to be found
as /etc/raidtab, telling you which drive's partitions are building an
array.

> Does it just try to grossly map them by size and 
> do they have to be of identical size on both
> drives of the RAID 1 or just bigger on ther mirror?
> Thanks in advance for any clarifications.
>                       Jack

http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/custom-guide/ch-raid-intro.html

Alexander


-- 
Alexander Dalloz | Enger, Germany | GPG key 1024D/ED695653 1999-07-13
Fedora GNU/Linux Core 1 (Yarrow) on Athlon CPU kernel 2.4.22-1.2188.nptl
Sirendipity 16:09:28 up 7 days, 13:54, load average: 0.72, 0.42, 0.30 
                   [ Γνωθι σ'αυτον - gnothi seauton ]
             my life is a planetarium - and you are the stars
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