Software RAID - wasRe: Adding new disks, include in volume group

[Gary Stainburn]

On Monday 13 June 2005 4:54 pm, Paul Howarth wrote:
> Scot L. Harris wrote:
> > I have built file systems across multiple drives before but that
> > was done during install of the system.
> >
> > BTW: how much of a problem is it with multiple drive file systems
> > when one of those drives fails?  Assumption here is that no raid is
> > being used for that volume.
>
> It's a big problem, and the severity depends on whether data you need
> to access is on the broken drive. I personally don't use non-mirrored
> multi-disk filesystems for anything of value, because I've had enough
> drives fail on me over the years that I feel the risk isn't worth it.
> However, I'd be more comfortable with it if it was say a pair of
> RAID1-mirrored drives added to a volume containing another pair of
> RAID1-mirrored drives (i.e. four drives in total). That could survive
> one (or possibly two) drive failures. You could mix and match with
> different RAID setups if you have lots of drives.

I've meant to look into RAID and plan to do so soon.  Based on what I've 
just read on the LVM howto you've pointed me at, you can do striping 
using LVM which *could* improve performance.  What is your opinion on 
using 2 drives for a LV with striping combined with 2 drives for RAID1 
mirroring (or 1 double size drive).

This setup would be on a standard motherboard with 2 IDE controllers and 
4 (3?) IDE drives.

What are people's thoughts on this.  
1) will it be complicted to set up/configure? 
2) How will it run day-to-day performance wise?
3) Would it be quick/easy to recover from a dead HDD?

>
> > And is a chance of such a failure a multiple of the drives in the
> > volume?  Or is it higher?
>
> I'm not a statistician but given an even distribution of data across
> the drives (which may not be the case), I'd think the chances rise
> linearly with each added drive.
>
> Paul.

-- 
Gary Stainburn
 
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