Hi,

 

I've been running unRAID for about two years now on a server built mostly from used components, including mostly older hard drives I had lying around. The storage is mostly used for media files, backups, cloud sync/storage back-ends, with a number of Docker containers and one Ubuntu server VM for various purposes,so nothing too fancy.

 

The server is capable of handling eight 3.5" and six 2.5" drives. I have seven of the eight 3.5" and all of the 2.5" slots populated, all hooked up to two eight-port SAS2008 storage controllers and currently run a double parity (2×3 TB 3,5" drives) set-up with a cache pool consisting of two SSDs (2×525 GB, 2.5") drives and a total of 9 TB of storage (which is about 90% full right now, so another reason to replace some disks). Parity and cache drive also are on a different controller each, for (hopefully) performance reasons.

 

One very old 3.5" 1 TB drive has recently shown a big number reallocated sectors, so this needs to get replaced ASAP. Also, one of the 2.5" disks only is capable of SATA I speed, and a few smaller (1-1.5 TB) drives are only capable of SATA II speeds. Also with the 3 TB parity drives, I am limited to putting in replacement drives <= 3 TB. In short, a number of drives will have to be replaced soon, both for storage/speed and age reasons.

 

I generally know to swap out one drive at a time and let the array rebuild data from parity and I am pretty sure the same goes for replacing the actual parity drives. As the 3 TB parity drives are still in good shape (as far as their SMART values go at least), I'd like to re-purpose them as data drives down the line.

 

The general idea from a cost/value point of view right now is to got with 8 TB parity drives and mostly 4 TB 3.5"/2 TB 2.5" drives as replacements over the next few months, bringing usable array capacity from 9 TB to 27-30 TB eventually. If I get a good deal on any 5-8 TB drives, I can also use those without a hassle.

 

Here's my plan, just curious if this is alright or I am missing something:

 

Replace faulty drive

1. Replace the dying old drive with a new 4 TB drive

2. Null 4 TB drive, add it to the array, let data re-build on it from parity (1 TB --> 4 TB drive, 11 TB array as I still only have 3 TB parity drives; will unRAID at that point tell me I can only use 3 of the 4 TB due to the size of the parity drives?)

 

Replace parity drive 1

3. Replace 3 TB parity drive with a new 8 TB drive

4. Null 8 TB drive, set it up for parity, let parity re-build (3 TB --> 8 TB parity drive, 8/3 TB parity drives)

 

Re-purpose old parity drive 1

5. Put former 3 TB parity drive in the one empty slot I still have, null 3 TB drive, add it to the array (<empty> --> 3 TB drive, 11 --> 14 TB array)

 

Replace parity drive 2

6. Replace the second 3 TB parity drive with a new 8 TB drive

7. Null second 8 TB drive, set it up for parity, let parity re-build - at that point, I'll have usable 8 TB of dual-parity (3 TB --> 8 TB parity drive, 8/8 TB parity drives, 14 --> 15 TB array, as I now can use the full 4 TB of the new disk instead of just 3 TB)

 

Re-purpose old parity drive 2

8. Replace some other 1 TB old age drive with the second former 3 TB parity drive

9. null 3 TB drive, add it to the array, let data re-build from parity (1 TB --> 3 TB drive, 15 --> 17 TB array)

 

Replace other old/slow/small disks

9. Replace old drive with new drive, null new drive, add it to the array, let data re-build from parity (depending on what gets replaced, 17 --> 17.5-30 TB array)

10. wash, rinse, repeat

 

Anything I am missing or not thinking of?

You will have to replace both 3TB parity drives before you add that first 4TB drive.  Any parity drive must be larger than the largest data drive!