Small capacity HDDs in RAID??

None. Areal density (more GB per unit area) is better as this means faster accessing of data (simplistically). Therefore big drives which use big platters are better.

However - your question depends on the RAID used. If RAID0, you want small drives because if it goes kaput, then you are more than likely to have less data to lose - and even that isn't a good reason.

I assume by small here you mean up to 80GB and large as 250GB and over. The middle ground is excluded.
 
Yeah, I've noticed a lot of systems which run RAID, (mirrored or Striped) tend to use 80gb or less and use large external capacity HDDs for documents etc. I assume that if its mirrored then its quicker access to data and striped is basically data back up of main drive? Is that RAID 0 and 1 respectivley? Or is the other way round?
 
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Wrong way round. RAID0 is data striping where the data is split between the two drives to speed reads and writes. Mirroring (RAID1) puts the same data on each disk so if one fails no data is lost but there's no speed improvement over a single disk.

There is no real benefit in having 2 small disks in RAID0 compared to two large disks in RAID0, there is however a speed improvement to be gained from having a pair of 80Gb drives in RAID0 vs a single 160Gb drive (assuming the same model of disk). You do however have to take into account the potential risk of data loss through drive failure with RAID0 so most folk will end up with a third drive for backups etc.
 
Actually you can get a small increase in read performance with RAID1 with certain controllers as there's 2 copies of the data available and so it's possible for the controller to read different bits of the file from different drives to increase read performance. Write performance is obviously no better than one drive though.
 
Trippynet said:
Actually you can get a small increase in read performance with RAID1 with certain controllers as there's 2 copies of the data available and so it's possible for the controller to read different bits of the file from different drives to increase read performance. Write performance is obviously no better than one drive though.
Hey, that's my line!

I still haven't used a controller which does that on RAID1 though (or maybe it does but it is so small, it is almost negligible).

RAID1 generally halves the write speed on bog standard controllers as the data is written and checked on both HDU's.

But this is where RAID0+1 and RAID10 come in.... ;) (I have purposely not mentioned RAID5 or 6 because controllers which do that properly are expensive).
 
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