Re: [gentoo-user] [OT] Disk recommendations?

[Peter Humphrey <peter@humphrey.ukfsn.org>]

On Sunday 10 April 2011 12:53:39 Stroller wrote:
> On 10/4/2011, at 8:50am, Peter Humphrey wrote:
> > ...
> > I'm just speculating at the moment, from a dabbler's point of view; what
> > benefits would accrue from switching from RAID-1 to RAID-5 or above?
> > And, in particular, what are the comparative virtues of the Samsung
> > disks?
> 
> In your previous message you mention "adding robustness", I don't think
> you'd change from RAID1 in that case.
> 
> RAID5 is less redundant than RAID1, but offers more space per drive.
> 
> Either will continue to run if one drive fails, but RAID5 consists of more
> drives (each of which has the potential for failure).
> 
> RAID1 has 2 disks and offers up to 1/2 redundancy. 1/2 your disks can fail
> without loss of data.
> 
> RAID5 has X disks, where X is more than 2, and offers upto 1/X redundancy.
> If more than 1 drive fails then your data is toast. This inherently allows
> for data loss if more than only 1/3 or 1/4 (or less - 1/5 or 1/6 if you
> have enough drives in your system) fail.
> 
> RAID6 needs an extra disk over RAID5 (at least 4 total?), and allows 2/X of
> them to fail whilst still maintaining data integrity.
> 
> I guess that theoretically RAID6 might be more robust than RAID1 but
> realistically one would probably use RAID1 if the volume is intended to be
> a fixed size (system volume), RAID5 or RAID6 if you want to be able to
> easily expand the volume (add an extra drive and store more data simply by
> expanding the filesystem). Other kinds of RAID (10, 50 &c) may be more
> suitable if read or write speed is also important for specialist
> applications, but you say you're only interested in home workstation use,
> not the datacentre.
> 
> Note that I only consider hardware RAID - others may be able to give advice
> more suited to Linux's software RAID.
> 
> I use RAID5 for my TV recordings and DVD rips. There's a famous article
> claiming RAID5 is worthless considering the size of current hard-drives vs
> uncorrected error rates (which manufacturers express per million or
> billion bits). I'm sceptical of the article, but nevertheless I guess I'm
> starting to get paranoid enough I'd prefer RAID6. Unfortunately my
> hardware RAID controller doesn't support it, so I guess I'm saved the
> expense. :/

Useful info - many thanks!

-- 
Rgds
Peter