Mailinglist Archive: opensuse (2835 mails)

[Bob Williams <linux@xxxxxxxxxxxxxxxxxxxxx>]

On Wednesday 24 December 2008 20:59:58 Rob OpenSuSE wrote:
> 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?
Good question.

> 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.
System stuff will be on its own disk.

> 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.
I think your point about long fsck times is valid, and one I need to consider. 
This is a personal home machine, not a data server. Some data in /home/bob is 
modified frequently, whereas other data is write once, read often. For 
example, I have about 380GB of music in flac format, which I had thought of 
putting on its own partition, possibly formatted as ext2.

> 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.
I dabbled in LVM a while ago, and got into trouble during an upgrade, so I've 
left it alone. I understand the principle and it certainly makes sense.

> 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).
I have an external SATA device that I can drop 3.5 inch drives into which 
works very well for rarely accessed stuff.

> 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.
So many choices. My head's beginning to spin :)

> 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.
I know that RAID is not a substitute for backup, and run an rsync script every 
day to deal with that. Is a corrupt file system on one partition of a disk a 
likely problem, or would other partitions suffer in the same way. IOW are we 
talking about a disk hardware problem or a higher level software problem? 

> 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.

I don't mind putting a bit of effort into planning a good strategy.

Many thanks for your lengthy and thought-provoking reply. And Happy Christmas 
:)

Bob
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Registered Linux User #463880           FSFE Member #1300
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openSUSE 11.0, Kernel 2.6.25.18-0.2-default, KDE 3.5.10
Intel Celeron 2.53GHz, 2GB DDR RAM, nVidia GeForce 7600GS

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