QNAP snapshot replica to remote NAS failing

[packeteer]

Hi folks,

After a few failed attempts at this I'm now seeking some assistance from the wider community.

I have 2 QNAP devices. First is an "older" TS-653A fully populated with 6 x 8 TB drives. This is my primary NAS and been keeping me going for the last 5 or so years. Herein known as NAS01.

It has two thick volumes. One volume is used for data I don't care about (aside from local snapshots to protect it) and the other volume is has the things I'd like to protect - which is backed up to a cloud service offsite and I used to have an old Netgear ReadyNAS for local backup using rsync. I recently came into possession of a TS-653D fully populated with 6 x 4 TB drives. Even though this is a newer model, I don't want to move the disks around to begin using the newer NAS as my primary (at least not right now). Herein known as NAS02.

So here's my problem. I'd like to use NAS02 as a snapshot vault for the volume I care about from the primary NAS01. Worth noting both NAS's run QTS 4.5.3.1652 and both use RAID-6 in a single RAID group. NAS02 reports 14.52TB capacity (210.6 GB Sys Reserved and 14.3 TB Free. No volumes have been created.

The first time I tried the snapshot replication, the wizard didn't let me continue after running the "test" button as it reported the destination didn't have enough space. I shrunk the volume down on NAS01 to 14.5 TB and re-ran the replication job - this time passing the "test". I ran the replication job and sadly it failed. - not enough space. I then shrunk the volume again to 13.85 TB - retried and it still failed.

So now I'm kind of stumped as I'd like to maximise the amount of space I can use to replicate from NAS01 to NAS02, but I don't know why the snapshot replication continues to fail with the error not enough space. Is there something about the snapshot itself that perhaps I'm not accounting for? Anything else I should consider/take note of?

Apologies if I've not supplied enough detail/initial info to help. I'm not that technical but I can get around the CLI if needed.

Thanks for any help/suggestions/tips etc.

Cheers,
P.

[P3R]

If you run a thick volume on the main NAS, the replica will be the complete volume size (not the actual data size) and in addition to that you need space for the future snapshot generations. If using large scale snapshots, a thin volume is recommended as then the volume overhead will be much more limited. Try to convert to a thin volume if you use a thick volume now.

[packeteer]

Thanks for the explanation P3R. I understood that thick volume was the full size of the volume (including free space) and I assumed the snapshots would sit on the same volume.

I'm not too keen to try converting from thick to thin just yet until I have a 100% local backup on another device. So I've taken a slightly different track.

NAS02 storage pool was re-created with RAID-5 (was RAID-6 before). I figure having RAID-6 on my primary NAS will be sufficient protection for "live" data and RAID-5 will buy me enough protection for the local backup (and there is also a cloud in the mix - so pretty covered). Doing this gave me about 17.7TB of free space after I created a small volume (200 GB) for any applications etc. On NAS01 I have increased the critical data volume to 15TB. Once the RAID sync is done on NAS02 I'll re-do the snapshot replica. If that works then I'll revisit the thin volume approach you suggested.

Cheers.