Re: [MLUG] software raid conifg - fedora

["George B. Robb III" <EMAIL:PROTECTED>]

I have had drives fail due to lack of cooling (Two Western Digitals (120 
GB) and one Maxtor (200 Gb)  all were under warranty but, RAID saved my 
data...  For a home server either backups or RAID is a great and cheap 
way to go...  I can't agree more that mis-matched drives kill 
performance on mirrors.  DON'T use a 4200 and a 7200rpm together ;)

Google search for the keywords LVM and RAID...  Loads of howtos out 
there but, everyone has their own method for establishing their disks :)

George


Mark Haidekker wrote:

> On Thu November 10 2005 17:07, Dave Lloyd wrote:
>  
>
> > On Thu, 10 Nov 2005, Shawn Parker wrote:
> >    
> >
> > > when configuring a software raid in fedora core 4, how do you set up
> > > an "extra" disk for raid1? i have 3 80GB drives in my server. i would
> > > like to set up a raid1 (mirror) of 2 drives and use the 3rd as an
> > > extra drive incase one fails?
> > >      
>
> Yes, this is the strategy. You can set up one drive as "spare" that can be hot 
> added if another drive fails. 
>
>  
>
> > > how does one do this? do i configure the raid1 using all 3 drives and
> > > simply set the "extra drive" parameter to 1? do i clone hda to hdc and
> > > hdd so that each drive is *exactly* the same, first?
> > >      
>
> The third drive should match the first two.
>
>  
>
> > > i have no problem setting up a standard raid1 with just 2 drives...but
> > > i'm a little confused when using a 3rd for an extra in fedora's
> > > partition manager.
> > >      
> > Not that I have an answer, but I've got a question:  why do you want to
> > do this?  It's my experience that the second drive will not fail until
> > you can replace the first failed drive unless:
> >
> > 1) There's a hardware problem where drives of a certain age fail
> >   (mechanical, de-soldering of chips, etc.).
> > 2) Outside environmental influences.
> >    
>
> I would agree with that. If one drive fails, you'll realize the problem real 
> quick. There is still enough time to replace the drive before the second 
> drive also fails. I had that situation recently - the intact drive is still 
> intact. Furthermore, after drive replacement, no data was lost.
>
>  
>
> > My personal opinion, and my experience backs me up here, is that
> > operator error that causes data loss is FAR more likely than a disk
> > failure.  You're better off doing a weekly backup to your third disk and
> > sticking it in a file drawer than having a hot spare that can come in
> > and replace a failed volume.
> >    
>
> As I mentioned above, disk failures do occur, and I had a RAID case recently. 
> I was glad I had RAID set up on that server, but I did not miss the spare 
> drive.
>
> IMO, if you have 3 drives, configure them as RAID5. You'll get 160 MB, 66% 
> efficiency instead of 50%.
>
>  
>
> > Oh, and please, please do not mirror swap.  Mirroring really cuts write
> > performance, and if you start to write to swap, well, things will begin
> > to suck much more than a "normal" condition under which you write to
> > swap.
> >    
>
> Right - but having one swap partition on each drive is great. Actually, some 
> people recommend RAID0 for swap to speed it up.
>
> Mark
>
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>  


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