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
