TS 879 Pro - Different size discs - options

[SkipperDK]

Got an option to buy a second hand TS 879 pro. It comes with fairly new discs, but in two groups. 4 x 3tb and 4 x 4tb. My question is, can I set it up to run all 8 discs as one volume, and raid 6 them, or do they have to be in 2 volumes? I was hoping it was possible to run them as one big volume.

Thanks

[Kunzite]

Yes, you can use them in one RAID 6 array, but they will all be used as 8x3TB HDDs.
In a RAID array all the HDDs behave as if they have the same capacity as the smallest one. (unless something like Synology's Hybrid Raid is used, but we're talking about QNAP here, no such fancy schemes are available).

Storage pools (and volumes) are another layer over a RAID array. You can have a storage pool expanding over two (or more) RAID array, but careful with that, if any of the RAID array has issues you lose all the data in that storage pool.

I guess I'd use two independent RAID arrays with their own storage pool (and volumes), but let's see what the more experienced people have to say.

[SkipperDK]

Thank you.

Data safety is priority, which is also why I say one big volume, in raid 6, and always an extra disc on the shelf

Guess I better go find 4 more 4TB discs and swap inn then, if no one else has better options

[FSC830]

Actually I dont see why one large volume is safer than two or more smaller volumes?
You can set shares which points to volume1 and other shares which points to volume 2, from client view its \\NAS\share1 and \\NAS\share2 (SMB notation) and client do not know at which volume the data is physically stored.
Both (or more) volumes can reside inside a raid pool, no matter, what kind of raid level is used.
For 8 disks I would also use raid6, but the need for one or more volumes should be clarified by i.e. capacity, data separation or something else, but safety is IMHO not an item.

BTW: For data safety an external backup at a regular schedule is mandatory! Forum is full of posts "help, my data is lost..." and in no case a backup exists. Data loss is not only done by malware, NAS can break down, a blackout, other physical damage, theft, ... all can cause a data loss.
If a backup exists, you may have a downtime, but you will get your data back.
Think about this!

Regards

[SkipperDK]

So while I do not understand all about NAS and Raid for sure, I respectfully sort of kind of agree, and disagree, I think, if understand the raid system right, which i probably don't. If I run Raid 6 on 4 discs, there is two of them that are wasted space, and on 8 discs, it is still two, so i basically waste two discs on setting raid 6 up on 2 four disc volumes, so I only see the logic in one big volume. Or am i wrong? Safety wise, I agree it should be the same, but wasted space also counts as long as it doesn't compromise security.

Yes, I fully agree that an external backup is mandatory, and I have that taken care off. Just need to figure the backup procedure out For now it is stored on loose discs, and on the old 809 pro.

Thanks for the feedback!

[FSC830]

Cant understand the logic here .
Yes, with raid6 you will always loose the capacity of 2 disks.
If you create your raids as a static raidgroup, then the volume size matches the (logical) raidgroup size.
If you create the raids as a pool, volume size is flexible. At a pool you can create one or more volumes.

My idea is that all of your 8 disks will have the same size 8x4TB and a raid6 is configured.
And in this configuration it doesnt really matter if it exists one large volume or multiple smaller ones.
I cant see neither an advantage nor a disadvantage fo one large volume in respect of safety.

But in your configuration, one large volumes spanned across two raid6 groups is the same size as the sum of 2 volumes, one at each raid group.
So I cant pick the point why one large volume should be better!?

Regards

[SkipperDK]

Well, as I said, I am by no means strong in this. Pools and volumes are not something I have messed with much, and I was just under the impression that 2 volumes would need their individual raid setup, so that is where my reasoning came from. From what you say, i recon that is not so then.

Thanks

[Kunzite]

It's not something difficult, once you get them properly explained (which I'm not sure I can do ).
Let's put setting up a volume in steps:
- you would combine HDDs in RAID arrays (or use HDDs in Single mode; any combination is possible as long as you have enough disks). If the HDDs in a RAID array are not the same capacity, they'll all behave as if they have the capacity of the smallest one.
- you would create a Storage Pool on top of a RAID array (or Single HDD). You can have a Storage Pool expand over more than one RAID array, but think carefully if you want to do that.
- you would create exactly one Static Volume, or how may Flexible Volumes (Thin or Thick Volumes) you wish on top of a single Storage Pool.
- in each Volume you can create several Shared Folders. All Shared Folders in a volume share the space available in the volume.

QNAP's interface merges creating RAID arrays with creating Storage Pools, but they're not the same - Storage Pools are a layer above.

What you believed is right... for Static Volumes. Not so for Flexible Volumes, though.