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30. Appendix J: Example IV: Server with 4 Drives
This gives an example of using all techniques described earlier, short of RAID. It is admittedly rather complicated but offers in return high performance from modest hardware. Dimensioning are skipped but reasonable figures can be found in previous examples.
Partition sda sdb sdc sdd
---- ---- ---- ----
1 root overview lib news
2 swap swap swap swap
3 home /usr /var/tmp /tmp
4 spare root mail /var
Setup is optimised with respect to track positioning but also for minimising drive seeks.
If you want DOS or Windows too you will have to use sda1 for this
and move the other partitions after that. It will be advantageous to
use the swap partitions on sdb2, sdc2 and sdd2 for
Windows swap, TEMPDIR and Windows temporary directory under these
sessions. A number of other HOWTOs describe how you can make several
operating systems coexist on your machine.
For completeness a 4 drive example using several types of RAID is also given which is even more complex than the example above.
Partition sda sdb sdc sdd
---- ---- ---- ----
1 boot overview news news
2 overview swap swap swap
3 swap lib lib lib
4 lib overview /tmp /tmp
5 /var/tmp /var/tmp mail /usr
6 /home /usr /usr mail
7 /usr /home /var
8 / (root) spare root
Here all duplicates are parts of a RAID 0 set with two exceptions, swap which is interleaved and home and mail which are implemented as RAID 1 for safety.
Note that boot and root are separated: only the boot file with the kernel has to reside within the 1023 cylinder limit. The rest of the root files can be anywhere and here they are placed on the slowest outermost partition. For simplicity and safety the root partition is not on a RAID system.
With such a complicated comes an equally complicated fstab file.
The large number of partitions makes it important to do the fsck
passes in the right order, otherwise the process can take perhaps
ten times as long time to complete as the optimal solution.
/dev/sda8 / ? ? 1 1 (a)
/dev/sdb8 / ? noauto 1 2 (b)
/dev/sda1 boot ? ? 1 2 (a)
/dev/sdc7 /var ? ? 1 2 (c)
/dev/md1 news ? ? 1 3 (c+d)
/dev/md2 /var/tmp ? ? 1 3 (a+b)
/dev/md3 mail ? ? 1 4 (c+d)
/dev/md4 /home ? ? 1 4 (a+b)
/dev/md5 /tmp ? ? 1 5 (c+d)
/dev/md6 /usr ? ? 1 6 (a+b+c+d)
/dev/md7 /lib ? ? 1 7 (a+b+c+d)
The letters in the brackets indicate what drives will be active
for each fsck entry and pass. These letters are not present
in a real fstab file.
All in all there are 7 passes.
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