I decided to write another paper that covers setting up a raid-1
computer :-) As always it is a lot of work. Here is the start of it.
Please find errors and such and bring them to my attention. The paper is
about 1/3 complete.
A raid-1 configuration is defined as two Hard Drives (HD) having the
same computer software on each of them. If one HD fails the other will
continue to run and the computer will operate as if nothing had happened.
Most of what is here is from an email of Jeffrey Ross who is a
member of the Fedora Users List. I have just used some examples and
re-ordering to suit my way of thinking.
There are some special raid configuration software. One is "fdisk"
and with that you can make partitions that have the special fd
configuration. The other is called "mdadm" and it is written to be just
a raid technical assett. Read man mdadm to see how capable it is.
Here is what you MUST do.
1. Your current HD and F7 partition is /dev/sda5 and your new HD will be
/dev/hdbx where x is a number from 1 to 7. The first thing to do is
decide how to lay out the many partitions it can look like this:
/dev/sdb1 = /boot
/dev/sdb2 = /usr
/dev/sdb3 = swap
/dev/sdb4 = extended partition
/dev/sdb5 = /var
/dev/sdb6 = /
/dev/sdb7 = /home
The partition size you find out by using "du -ch". For example to
see how big /usr must be in a Terminal cd /usr and there type $ du -ch.
On my F7 /usr is 3.4 Gbytes. So /dev/sdb2 should be 4 Gbytes or larger.
Make the partitions with "fdisk". To do this you need to open a root
Terminal and use # fdisk /dev/sdb. If your /dev/sdb is a new HD it will
not show any partitions when you say p. On my old HD it shows this:
Command (m for help): p
Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 1217 9775521 83 Linux
/dev/sdb2 1218 1945 5847660 83 Linux
/dev/sdb3 1946 1961 128520 82 Linux swap / Solaris
/dev/sdb4 1962 18534 133122622+ 5 Extended
/dev/sdb5 1962 7060 40957686 83 Linux
/dev/sdb6 7061 12159 40957686 83 Linux
/dev/sdb7 12160 18534 51207156 83 Linux
Command (m for help):
As you can see the HD has 160 GB and it has 5 Linux file systems and a
swap partition and /dev/sdb4 is an Extended partition.
For our raid-1 work we want all partitions to be Linux raid
autodetect which you get with "fdisk" when you make a new partition.
Here is how it is done:
Command (m for help): n
First cylinder (12160-18534, default 12160):
Using default value 12160
Last cylinder or +size or +sizeM or +sizeK (12160-18534, default 18534):
16000
Notice that I choose 16000 to end the partition. If you look the new
partition has 30 GB total space.
/dev/sdb7 12160 16000 30852801 83 Linux
The type of partition is wrong. We don't want Linux. We want raid and
that is done this way:
Command (m for help): t
Partition number (1-7): 7
Hex code (type L to list codes): l
Hex code (type L to list codes): fd
Changed system type of partition 7 to fd (Linux raid autodetect)
Command (m for help): p
Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 1217 9775521 83 Linux
/dev/sdb2 1218 1945 5847660 83 Linux
/dev/sdb3 1946 1961 128520 82 Linux swap / Solaris
/dev/sdb4 1962 18534 133122622+ 5 Extended
/dev/sdb5 1962 7060 40957686 83 Linux
/dev/sdb6 7061 12159 40957686 83 Linux
/dev/sdb7 12160 16000 30852801 fd Linux raid
autodetect
Command (m for help):
To save what we have shown here type w as in write the new things. I
used q which means quit without saving.
In our example we have to do the same thing for /dev/sdb1 through 7
and it is easy to do and will not take long. Now our new HD is set to be
a raid-1 HD.
2.
Now back to the old HD. We need to make the raid partition numbers which
to make life simple will be the same as the new HD. We do this with
"mdadm" as follows:
mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb1 missing
mdadm --create /dev/md2 --level=1 --raid-devices=2 /dev/sdb2 missing
mdadm --create /dev/md3 --level=1 --raid-devices=2 /dev/sdb3 missing
mdadm --create /dev/md5 --level=1 --raid-devices=2 /dev/sdb5 missing
mdadm --create /dev/md6 --level=1 --raid-devices=2 /dev/sdb6 missing
mdadm --create /dev/md7 --level=1 --raid-devices=2 /dev/sdb7 missing
--
Karl F. Larsen, AKA K5DI
Linux User
#450462 http://counter.li.org.
