| if i understand correctly, whilst i will shortly be allowed to mix 4s and | 9s, i won't be allowed to use a full set of 9s - in fact, i'll be limited | to 21*4 + 3*9 for data, with one hot spare and one parity, leaving me two | disc slots i can't use.
I believe this is due to file system limitations; the 220 was limited to 50G, the 330 to 100G. Only the 540's were to be able to raise the file system limit by using 9G drives.
Unless I'm sorely mistaken, the F540 is similarly limited to 200GB.
This could be a technical limitation (doubtful) or a marketing imposed one (very probable).
I won't argue against there being a marketing component to our logic, but there really is at least some technical reasoning -- the longer it takes to reconstruct after a drive failure, the greater the exposure there is to a multiple drive failure and consequent loss of data. We therefore make sure that a given filer has sufficient CPU performance to reconstruct a fully-configured array in no more than a target amount of time. (I think the target is 8 hours but it's late and I'm picking that from non-parity neurons. ;-))
For an F330, 100GB is the limit beyond which the window of exposure to multiple drive failures becomes unacceptably long. Therefore, even though Tom's F330 is not performance-bound *in normal operation* we won't support >100GB on it.
Perhaps there may be a better explanation for this.
I hope my version is at least a little better.
-- Karl