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Re: raid + lvm setup



On Sat, Dec 09, 2006 at 09:13:51PM -0500, Douglas Tutty wrote:
> On Sat, Dec 09, 2006 at 05:52:08PM -0800, Andrew Sackville-West wrote:
> > On Sat, Dec 09, 2006 at 08:11:00PM -0500, Douglas Tutty wrote:
> > > 
> > > Then LVs for everything including swap.
> > 
> > my genuine curiousity question is why you would bother to put swap on raid? I
> > suppose if you had a lot of swapping going on and a drive failed, it
> > could be catastrophic, but that's the only reason I can see. And this
> > may be more than enough reason... I wonder what the overhead for that
> > it though? 
> 
> That is the reason.  The idea is that if a drive fails I can still
> shutdown gracefully, pop in a new drive (until SATA is hot-swap), reboot
> into the degraded raid1 (in single if /home is not also on raid1),
> reformat the drive, and get the raid1 resyncing.
> 
> I haven't noticed any overhead, although I have on GB of ram and
> actually haven't swapped yet.  Swap is just there in case and for /tmp
> on tmpfs which won't be any more overhead than having /tmp on raid1.

lucky devil! no that makes sense to me. And if you're going to do
video editing, swap might become real crucial real quick.

> 
> > 
> > [...]
> > > 
> > > Does this seem like a workable/wise plan or here there be dragons?  Is
> > > there any reason to think that 20 GB is too small for a fully installed
> > > workstation including swap and /tmp (everything but /home)?
> > > 
> > 
> > certainly seems workable to me, but I don't really know about these
> > things too much. Certainly, though (depending on how big your swap
> > is), 20G is enough for the system.
> > 
> 
> Is 20 G overkill?  Would 15 G be fine?  The risk is that if I guess too
> small, one can't extend a raid1, I'd have to make another raid1 and add
> it or some such gymnastics.  In this case, drive space is cheap.
> 
> I eventually want to get into video editing, watching TV and movies, and
> Lyx.  I don't know how much disk space they use.  How much does a fully
> loaded system take (I've never before had the horsepower to bother with
> such stuff).
> 

well this particular box has only been deb for about 6 weeks and I
haven't had time to get it all filled up yet, but the system (not
counting swap and home) is currently using 1.9G. I think my main box
at home is using about 4G in reality. so 20G's in my opinion is
probably overkill BUT since you're putting LVM over RAID, you can
always shrink those volumes later and add the extra raid into the rest
of your lv's... maybe?

A

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