When you increase the storage capacity of your server, how much additional capacity do you add?  50%?  100%, 200%?  i have 9 TB version 5.0.5 "Plus" system with mostly 2 TB and 1.5 TB drives (5 data, 1 parity, 1 cache)  It is nearly 50% full (after about 18 months of operation).  I cannot decide if I want to replace 2 TB drives with 3 TB drives or sit tight a few months and look for a deal on some 4 TB drives.  Comments?   

@70-80, double capacity.

When you increase the storage capacity of your server, how much additional capacity do you add?  50%?  100%, 200%?  i have 9 TB version 5.0.5 "Plus" system with mostly 2 TB and 1.5 TB drives (5 data, 1 parity, 1 cache)  It is nearly 50% full (after about 18 months of operation).  I cannot decide if I want to replace 2 TB drives with 3 TB drives or sit tight a few months and look for a deal on some 4 TB drives.  Comments? 

 

I have a 27tb array at the moment. Whenever I have a few TB left (like now: 4tb left). I buy a new disk, I try to buy the largest size available (unless that is ridiculously expensive), I am now looking at a 6TB WD RED (unless the 8TB comes out soon), I then make that drive my new parity drive and start using the previous parity drive (in my case a 4tb) as data drive.

 

Whenever I need to add a drive and the parity does not need to be upgraded (like, whenever the largest drive is still to expensive) then I just add a drive. I also try to get rid of the oldest one.. At the moment I still have 3 3 year old 2TB's, one of these is starting to show errors, so I will try to move that out of the array before it gets redballed.. In this case I might buy 2 6TB's, with the extra one used to get rid of the 2tb's.

Entirely a personal decision.

 

There are many factors to consider ... how many SATA ports do you have;  how many drives can your case hold;  etc.

 

With the mix of drives you have, I presume your parity is currently only 2TB.    So I'd definitely upgrade that as your next move, so future drive purchases can be larger drives.    And do that SOONER rather than later ... if you've upgraded to a larger parity drive, then when a drive fails (it WILL happen someday) you can replace it with a larger drive.    There's a process that allows you to upgrade your parity drive and use the old parity drive to replace a failed drive; but it's far better to now have to do that.

 

At today's prices, I'd get a 4TB WD Red for your parity drive ... and since you're only using 50% of your capacity, that's the only chance I'd make in the near future.  If you have a spare drive slot, you could also add the old parity drive to the array so you'd have even more spare space.    Then, as you need more space in the future, just add additional 4TB drives (or replace your oldest/smallest drives with 4TB units).

 

I typically buy a pair of disks when my available space is running low and I see a good sale. It is not as a % of my disk space.

 

Look at the BackBlaze reports - which are not perfect but do provide some good reliability statistics. THere is a sticky in the drive subforum.

 

Gary is a big WD Red fan, but the reports don't give them high marks. Maybe the vibrations on the BackBlaze pods hurts them more than a typical unRAID setup and that is the disparity. I recommend HGST (previously Hitachi) drives as they have been rock solid for me and they get superior scores by BB. They used to be priced the same or lower than WD and Seagate, but now are demanding a premium due to their reliability. You can still find a good price on them from time to time. But a pain free unRAID experience is worth a premium to me, and as stingy and price conscious as I am, when it comes to disks, I find myself reluctantly plunking down an extra Benjamin or two for the HGSTs.

... They used to be priced the same or lower than WD and Seagate, but now are demanding a premium due to their reliability.

 

The cost difference is very minor ... e.g. at the moment a 4TB HGST NAS unit is $169.99 and a 4TB WD Red is $165.99.  I don't think this difference is "... due to their reliability"    [in fact, the BackBlaze report shows the 4TB Reds have been MORE reliable than the 4TB HGSTs]

 

The BackBlaze reports are a reasonable source of info, but are definitely flawed.  If you look at their current data (Feb '15) you'll see that Seagate's reliability is MUCH worse than either WD or HGST.  Guess which drives BackBlaze buys the most of ... Seagate !!    They're driven entirely by cost vs. reliability => and since their pods are all RAID-6 units that are also backed up across data centers (thus mitigating data loss concerns), they've found that even with the higher replacement rate it's still economical to buy the Seagates.

 

I don't buy WD Reds for price reasons ... I've been buying them since they were first released, when a 4TB unit was ~ $250.    But they've been exceptionally reliable => in fact, I've never had a failure except for the initial testing of some drives that were in a VERY poorly packed box of drives I received from Newegg  [see picture below].    I prefer them over the HGST's simply because they run notably cooler, thanks to their slower rotation.  I don't think the 7200rpm speed of the HGST's is needed in a NAS environment, so I'd rather have the cooler, lower-power Reds.

 

By the way, BackBlaze has only bought one pod worth of the 4TB WD Reds ... but to date (not quite a year) they've had ZERO failures.    I don't think the HGST's can beat that 

 

 

This was the box of drives I got a couple years ago that had about half a dozen WD Reds in it ... ONE of those drives failed my initial testing, so I had it replaced.    The other 5 from that shipment ... along with all the others I've purchased before and after that (a couple dozen) are all still working perfectly, with zero reallocated sectors; zero pendings; etc.    I took the pictures from my front entryway, where UPS left the box exactly as you can see it.    I don't consider a failed drive in that box the fault of WD  :)

 

 

 

... Another view of that box

 

I had a similar delivery this weekend from UPS who handed off to USPS for final dropoff. Surprised the drive actually passed 2 preclears without issues. (only 1 drive in the entire box -- bare drive in plastic eggshell with some bubble wrap in the box).

 

I think ill be picking up the rest of my drives in person now. Especially since best buy will pricematch amazon and newegg. Even if its an extra $10, thats easier than drive failure down the line

 

 

Regarding OPs question...

I have a spreadsheet with my current setup and I punch different scenarios side by side to see what the cost would be to add more GB. Since my server is under 3TB and I only add about 150GB a month, its still economical for me to use 2TB drives.

 

But if I was in your shoes, Id start looking for deals on 4TB, or 6TB if you can budget it.

 

And let me know if you want to sell any of your 2TBs for a good price. I have room for 3 to replace 400 and 500 gb drives that are old. 

... Since my server is under 3TB and I only add about 150GB a month, its still economical for me to use 2TB drives.

 

I assume you have a 2TB parity drive, and that's part of your computations.  Otherwise, it's almost certainly more economical to add 3TB drives, as the cost/TB for these is generally lower than for 2TB units.  Of course if you're buying used drives, the math changes ... but for most drive series (WD Greens, WD Reds, Seagate NAS, HGST, etc.) the 3TB units have slightly lower costs/TB than the 2TB units.    For example, a new 2TB WD Green (EZRX) is $80 today at Newegg ($40/TB) ... while the 3TB version is $95 (with a $5 promo code) or $100 without the promo code ($31.67 - $33.33 /TB).

 

Obviously if you have a 2TB parity drive, then the need to upgrade your parity influences the costs ... although even then I'd be inclined to buy a 3TB drive the next time you need more storage and replace the parity drive -- adding the old parity as additional storage.    That would be a one-time "penalty", but would then let you use 3TB drives moving forward.    At the costs noted above, the "penalty" would only be $15, since you can buy a new 3TB EZRX for only $15 more than the 2TB version.    And you'd more than recover that penalty the first time you added a 3TB data drive.

 

 

... Since my server is under 3TB and I only add about 150GB a month, its still economical for me to use 2TB drives.

 

I assume you have a 2TB parity drive, and that's part of your computations.  Otherwise, it's almost certainly more economical to add 3TB drives, as the cost/TB for these is generally lower than for 2TB units.  Of course if you're buying used drives, the math changes ... but for most drive series (WD Greens, WD Reds, Seagate NAS, HGST, etc.) the 3TB units have slightly lower costs/TB than the 2TB units.    For example, a new 2TB WD Green (EZRX) is $80 today at Newegg ($40/TB) ... while the 3TB version is $95 (with a $5 promo code) or $100 without the promo code ($31.67 - $33.33 /TB).

 

Obviously if you have a 2TB parity drive, then the need to upgrade your parity influences the costs ... although even then I'd be inclined to buy a 3TB drive the next time you need more storage and replace the parity drive -- adding the old parity as additional storage.    That would be a one-time "penalty", but would then let you use 3TB drives moving forward.    At the costs noted above, the "penalty" would only be $15, since you can buy a new 3TB EZRX for only $15 more than the 2TB version.    And you'd more than recover that penalty the first time you added a 3TB data drive.

I only buy on sale, so last week i picked up a 2TB for $65, which is right around the same $/TB as the 3TB. My plan is to hold out until 4TB or 6TB come down a little in price, and then make the jump. Upgrading from 2 to 3TB just really doesnt justify the change (IMO) unless you are just adding extra disks. I dont think ill upgrade to Pro in the foreseeable future, and most of my drives are hand-me-downs from retired 2007-2011 computers, so it would make more sense for me to replace disks rather than to add more to the array (Plus, adding disks would also require me to get another sata card, as well as get a 5 in 3 drive bay to store the extra disks.

 

Plus, since my total array is under 3tb, its better fault protection to be spread between multiple smaller disks in case of double drive failure (or oops i didnt know what i was doing and deleted a disk -- errors).

Agree that with a total storage requirement that's so modest it's easy to just use 2TB drives that you get on sale or via used drive sales.    It's also much easier to backup an array that small, as you can backup the entire array to a single external drive.