Volume size calculation ?

[Lewis]

Hi,

I wonder how is volume size limit calculated in DS series. I have DS 1817+ but it's same for 2021 models from what i can see volume size limit is 108TB.
I'm using SHR-2 so i wonder is Volume size calculated as all 8 drives or just 6 drives (since 2 drives are used for parity in SHR-2) ?

Basically what i wonder is can i plug in 8*16TB (128TB) with not exceeding limit of 108TB since it would actually have 6*16TB=96TB of actual/usable storage due 2 drives is used for parity?

Thanks

 

[fredbert]

You use one or more drives to build a storage pool. That storage pool will have a maximum size, based on the RAID type you used. When you created the storage pool you will have had the option to allow multi-volumes, or not.

So if you have eight drives in SHR-2 then the storage pool will have usable space of six drives. In SHR-1 it would the space of seven drives. In JBOD it would be all eight drives.

Volumes are built on top of a storage pool and it's an individual volume that has the limit.

 

[Lewis]

Thanks for lengthy answer but kill me if I understood what is the solution in my example .
I'd appreciate simple(r) answer if possible::

1. 8*16TB will work fine as one volume in SHR-2 setup (96GB volume)
2. Or i will have to create 2 volumes (108Gb + 20GB)?

Thanks and i apologize in advance for not understanding fully your previous answer ..

 

[fredbert]

1. Yes

 

[fredbert]

If you're going to be using a NAS then it would be useful if you understood the relationship between the hardware (drives), the RAID structure, and the usable file system volumes. The Synology limit is on the volume, not the raw storage of the drives, and not the usable storage created by a storage pool.

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If you had a NAS with 12x 16TB drives then you could create a SHR-2 storage pool giving a usable space of 10x 16TB (160TB). To be able to use all this space you would have to have at least two volumes, e.g. 108TB and 52TB.

Of course then are other options for configuring the drives, such as multiple storage pools each with a single volume.

 

[Lewis]

Thanks .

Also yes I know I can have multiple volumes but currently it's not practical for my use case, that's why I asked so I can be sure how it calculates with SHR-2 and I wanted to be sure I can replace my 8TB and 10TB drives with new 16TB and still have it all single volume.
I'd hate it if after waiting for weeks raid rebuilds (one by one of course) and then find out I have unused space which I need to set as different volume for which I don't have usage (yet) .

Thank you again.