Re: [opensuse] Partitioning question

2008/12/24 Bob Williams <linux@xxxxxxxxxxxxxxxxxxxxx>:
ATM my /home partition is 1TB on a RAID1 mirrored array. I am going to add a
third 1TB disc and convert the array to RAID5, which will give me 2TB usable
space.

Is there any performance/safety advantage to breaking this arrangement into
several smaller partitions or can I leave it as a single partition?

Performance of what though?

For High performance RAID 10, striping 2 mirrors is faster, and more
resilient than RAID 5; especially if you will be writing
non-sequentially with in place database files. You may run into
issues if system partitions were on a 3 disk RAID 5, where with
straight mirroring you can always mount the standard device in that
situation if needs be, and move back to RAID 1 later. RAID 5 made a
lot of sense, when large (for time) reliable disks were very
expensive, and cheaper ones arrayed could give better price capacity
and performance figures. Presumably you do have another disk used for
system stuff.

When you're just storing and streaming back big multi-media files
then, you have not too many problems performance during usage
accessing files. Your main risk is very long fsck(8) times on some
boots. There can be other advantages to partitioning, it can avoid
very long seeks, if files that are accessed simultaneously find
themselves in far apart cylinders. They're easier to manage.

You can get a lot of advantages of partitioning, without the
flexibility disadvantages if you use the LVM. I'd much prefer to get
most data out of /home, and keep that for personal settings, and
scratch space, rather than 'archive' material, and big downloads etc
etc. LVM allows snapshots, which might simplify your back up
immensly, if backing up 2TB is every simple.

Other considerations might be to keep large but rarely accessed stuff,
eg) disk backup files from other systems on their own disk, that
spends a lot of time spun down, rather than spinning. Utilising more
disk arms by spreading files, can also improve performance, without
using LVM that tends to result in many disk partitions. A technique I
use often is bind mounts to splice in, thinks like web proxy cache
onto the right directory in /var which I try to keep smallish size,
but with plenty of free space, for fast writes and fragmentation
avoidance (helps YaST & rpm).

Partitioning also gives you a chance to deploy filesystems to tasks
that they're best suited. XFS is well liked. ext4 performed well in
Phoronix tests but is only just about to be become stable.

It is indeed safer not to have all your data in one massive pot.
Restoring smaller amounts of data in event of a corrupt file system or
an accident as root on the disk device, is far easier than one massive
filesystem. RAID is not a substitute for backup.

Downside of multilple partitions, is additional thinking and planning.
At the end of the day it has to be your choice, how you organise the
data storage, some ppl just want it 'simple' and are unwilling to put
any effort in to better organisation.
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