December 1, 201510 yr This may seem like a silly question but here goes. What is the point of having, say an 8TB drive as your parity drive, if your next largest drive is smaller than 8TB, say 6TB? Really, the only advantage to having an 8TB parity drive is to replace the parity data on an 8TB data drive, correct?
December 1, 201510 yr This may seem like a silly question but here goes. What is the point of having, say an 8TB drive as your parity drive, if your next largest drive is smaller than 8TB, say 6TB? Really, the only advantage to having an 8TB parity drive is to replace the parity data on an 8TB data drive, correct? Correct. If you have an 8tb Parity, but only up to 6tb Data Drives, the assumption is that you're ultimately going to be adding (or replacing) a data drive with an 8tb. In my case as an example, my two servers are both maxed out. One of them was all 3tb, and the other was a mix of 1 and 2 tb drives (2tb parity). After I completely ran out of space, what I did was replace the 3tb parity with a 4tb. This freed up a 3tb drive which I began using as parity on the 2nd server. The old 2tb parity I used to replace a 1tb data drive. Net result is that I bought a 4tb drive and only gained 1tb in space. But I am far better positioned for future upgrades (after I fill up that 1tb I'll replace another 3tb with a 4tb, move the 3tb over and replace another 1tb). At that point since I'll have a pair of 1tb drives, I'll make another server to utilize the pulled out drives so that I'm not losing any space.
December 1, 201510 yr Clearly if you don't ever intend to increase the size of your data drives, there's no reason to have a larger parity drive. Remember that the parity drive must be <= the largest data drive ... in other words it sets the limit for the size of your data drives. So, for example, in the system Squid noted, where he had all 3TB drives, when he wanted to start using larger drives, he needed to replace his parity drive with a larger drive, which sets the new max limit for his data drives. He chose to only bump it up to 4TB, but he could have used a 6TB or 8TB drive instead, and then his data drives could have grown to that new size. Bumping from 3TB to 4TB means that the new data drives can only be 4TB -- i.e. for the price of a 4TB drive he'll only gain 1TB of space. If he'd used an 8TB drive instead, then for the price of an 8TB drive he'd gain 5TB for each drive replacement. Personally, if I'd had the two servers he mentioned, I'd have put the new 4TB server on the smaller server (and left the all-3TB system along). Net result would have been the same -- i.e. buying a 4TB drive and only gaining 1TB => but he could then replace the 1 and 2TB drives on that server with new 4TB drives and gain a lot more space than he would by replacing 3TB drives with 4TB units.
December 1, 201510 yr Personally, if I'd had the two servers he mentioned, I'd have put the new 4TB server on the smaller server (and left the all-3TB system along). Net result would have been the same -- i.e. buying a 4TB drive and only gaining 1TB => but he could then replace the 1 and 2TB drives on that server with new 4TB drives and gain a lot more space than he would by replacing 3TB drives with 4TB units. A different reason for not going that route. (And the net result is still the same after using the 3tb's to replace the 1's).
December 1, 201510 yr ... And the net result is still the same after using the 3tb's to replace the 1's ... Yes, I noticed that ... but it requires two drive replacements instead of one; and I'd think it would make a lot more sense on the all-3TB array to bump parity to at least 6TB if you're going to move to larger data drives.
December 1, 201510 yr ... And the net result is still the same after using the 3tb's to replace the 1's ... Yes, I noticed that ... but it requires two drive replacements instead of one; and I'd think it would make a lot more sense on the all-3TB array to bump parity to at least 6TB if you're going to move to larger data drives. I'd do that if I was ultimately looking to downsize the amount of hard drives, and as a digital hoarder I just don't ever see that happening. I picked 4tb based upon its current bang for the buck, the amount of time required to fill the drives, a guess at how the prices are going to fall over the next year, etc etc etc. (And, since I bought that first 4tb the day after my wife was laid off, it was a fair amount less stressful to me to spend less money)
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