Migration shr1 to shr2

[Enquiries]

I just setup a 3x24TB shr1 volume in my new DS1825+. Since I will eventually populate it with more drive, up to 8, and larger (today it could be 28TB if I wanted), I am wondering how can I quickly and safely add bigger drives and convert to shr2. I understand that I need 4 drive minimum for shr2 and if I add less then 4 bigger drives I will lose space. My question is on the process to do it; I know how to calculate SHR1 & SHR2 volume capacity based on drives size.

[ed]

1. How do you safely convert your current SHR1 pool to SHR2 on the DS1825+?
Install a fourth drive first. Expand the pool with that drive and let the rebuild finish fully. Once Storage Manager shows four healthy drives in the pool, use Change RAID Type and select SHR2. DSM will convert the pool in place without needing to delete your volume.

2. How do you add larger drives without losing space or causing issues?
You can add larger drives at any time, and the pool stays protected. However, adding a single larger drive does not increase usable space. With SHR layouts, the system needs at least a pair of larger drives before it can raise the internal minimum drive size. Until that threshold is met, the larger drives behave as if they were the size of the smallest disk in the pool.

3. When does extra capacity from larger drives become usable?
For SHR1 you need two larger drives.
For SHR2 you need three larger drives.
Only then does DSM unlock additional space by increasing the usable base drive size inside the array.

To predict exactly how much space you will gain at each stage, you can test your planned drive combinations here:
https://www.synology.com/en-us/support/RAID_calculator