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. :/ Stroller.
