RAID questions (was Re: [TriLUG] Re: Dieing hard drive?)

[William Sutton]

I've been lurking here watching this thread develop, so I have some 
questions I'd like to pose to those of you with more expertise than I :) 

I have a spare system based on an Abit VP6, dual PIII 750, 512 MB RAM, 
etc, etc, that I've been piecing together.  After much diddling I've 
decided to give it to my parents as an upgrade for their PII 233 Compaq.  
This being for my parents, it'll need some variant of Windows (before all 
of you zealots on the list chime in, this question is still on-topic as 
far as the RAID thread goes, so please don't flame me).

I'd planned on using the board's on-board RAID features so that they have 
on-system redundancy for the important data (don't care about the OS, just 
certain files).  I'd also planned on using a couple of 80 GB Maxtor IDE 
drives (the on-board controller is IDE).

Questions:
1. Is RAIDing this puppy even a logical decision?
2. If I do want to use RAID, what level(s) do I want?
3. Do I want to use the on-board controller (this thread is starting to 
sound like the answer is no)?
4. If not, how does one implement software RAID on a system as spec'ed 
above?
5. Much earlier in this thread there was discussion of relative quality of 
older drives vs more recent drives.  For stability and durability in a 
system of this class (old :) 133 MHz PCI bus) what sorts of disk drives 
would you recommend?

Many thanks in advance to all who reply with helpful suggestions.

William Sutton
Huntsville, AL, TriLUG member

On Tue, 30 Nov 2004, Mike Johnson wrote:

> Aaron S. Joyner wrote:
> 
> > IMHYAO, Raid 5 is only a good choice if you are using a large number of 
> > drives, and can incorporate a hot spare or two - or if you really can't 
> > afford to sacrifice 50% of the capacity of the purchased drives.
> 
> For home fileserver use, RAID 5 should be fine.  RAID 5 suffers when 
> performance is needed.  For a home fileserver, that may not be an issue. 
>     We're not talking about editing large video files, so RAID 5 is 
> likely to be perfectly adequate.  Of course, it depends on how much 
> storage space you're looking for.  If 160GB is enough, then two 160GB 
> drives and RAID 1 would be great.  If you want 320GB, then three 160GB 
> drives in RAID 5 would be great.  If RAID 5 isn't fast enough, increase 
> the filesystem cache size and move on.  RAID 5 reads aren't as bad as 
> RAID 5 writes.
> 
> > I'd generally suggest the controller.  The advantage being that it gives 
> > you another set of IDE channels to attach those drives to (as you may 
> > need them since they is not going to be your only disks).  It also 
> > pretty-much ensures that you're going to have hot-swappable channels, 
> > which is a nice feature in a RAID setup, given that one of the main 
> > purposes of RAID is to keep things up and running should a disk die.  
> > Another consideration in the RAID 5 vs mirroring debate is that most 
> > cheap RAID cards can't do RAID 5, and it is a larger software hit to do 
> > the checksumming and other processing on the host system.
> 
> The biggest gotchya with RAID cards that many people seem to overlook is 
> that the on disk format of the actual bytes is specific to that 
> controller.  If your controller dies (it happens!), you -must- replace 
> it with an exact duplicate card, or you will not get your data back. 
> And there's nothing stopping a vendor from releasing a new version of 
> the card that uses a different chip without saying so on the box.  If 
> you go the hardware route, buy two of the cards, right off.
> 
> If you go the software route, then a controller failure is no big deal. 
>   You simply move the drives to a different system and you're golden. 
> Plus, don't most of us have a lot of spare CPU time on our fileservers?
> 
> Mike
>