[ILUG] Hardware RAID & partitions

[Wesley Darlington]

Hi all,

On Thu, Feb 03, 2000 at 10:13:43AM -0000, Jakma, Paul wrote:
> the partition magic programme is called resize2fs. ext2resize is GPL, and
> actually seems to work better than resize2fs. (eg it handles 4KB block fs's)

The implication being that resize2fs doesn't handle 4kb blocksizes
correctly. Eeeek. Scary! :-)

> > o If you /are/ reinstalling, consider raid 1. Keep, say, 
> > /home on one raid
> >   1 array and everything else on another. With swap on both. 
> > Me, I *despise*
> >   raid 5 for its awful write performance.
> 
> but RAID5 makes a lot more efficient use of disk space. Check in the RAID
> controllers setup utility for an option to set "Write-Back". This improves
> things greatly. ( but computer must be on a UPS).

Sorry, hadn't considered the possibility that somebody might do raid5
without writeback enabled. *Shudder*  

Even with writeback, any raid5 implementation I've used (*) has sucked. You
fill up the the writeback cache and everything goes dog slow. Even with,
say, 128MB of bb writeback cache, you can fill it up too easily, and
it empties at a handful of megabytes a second. :-(

(*) Of course, I've only ever used sucky raid5 implementations. :-)  
    DPT and Megaraid, and a couple of yellow pack dedicated external
    arrays. What are the others, like Mylex and ICP like? How about
    dedicated external boxes like compaq's storageworkses...?

As for the disk space issue, disks are cheap.  Raid5 is great where you
have far too much `legacy' data which needs to be accessible, but which
never gets changed. I don't believe it's appropriate for partitions like
/tmp, /var and even /home, especially on a megaraid with a small amount
of writeback cache. And as for swap... :-)

Wesley.