Does thin volume not auto expand when needed?

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Prizm78
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Does thin volume not auto expand when needed?

Post by Prizm78 »

Hi

I have been reading this how-to about thin and thick volume, but I am still confused about it ( https://www.qnap.com/en/how-to/knowledg ... ick-volume ).
Thin Volumes allocate space in the storage pool as data is written into the volume. Only the size of data in the volume is used up from the pool space, and free space in the volume does not take up any pool space. If data is deleted from the volume, that space can be freed and given back to the storage pool free space.
So to my understanding, is that when i setup a thin volume it should grow in size as long as there is space in the storage pool?

This is my setup:
QNAP TS-453D (Firmware 4.5.4.1723)
4x6TB Seagate Ironwolf (One single Raid group and RAID5)

This what i have done:
1) Storage Pool (utilize all the space available)
2) I have setup multiple volumes (Dashboard-Storage&Snapshots->Storage->Storage/Snapshot->Create->New Volume
Setup Thin Volume.png
3) I then select "Thin volume" and click Next, from there i give it a name, set a size and follow default suggestion of 32K.
Setup thin volume - Configure.png

So my question actually boils down to my understanding of the how-to guide AND the quoted text in the beginning.
1) How i understand this is that a thin volume should expand when more data is written to it
2) The size I set is just a initial size and not maximum
3) Have i completely misunderstood how thin volume works?

I simply want that each of the thin volumes to pull the needed resources (space) they need from the Storage pool in the system, when they need it.

4) Could it be that the seize i set during configuration of thin volume is the maximum size its allowed to take from the pool? So if i really wanted flexibility i should set this size much-much higher. And then carefully monitor the actual usage of the data used from the storage pool. To my understanding is that if I over-provisioning the volumes compared to storage pool much can go wrong.
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dolbyman
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Re: Does thin volume not auto expand when needed?

Post by dolbyman »

A thin volume is still limited to it's given size.

The allocation will grow when data is written to it, that's why they can be over-provisioned.

Over-provisioned thin volumes have a very limited usage scenario and the actual pool space needs to be monitored otherwise will cause issues.

For 85% of all users, a single static or thick volume will be just what they need (you could work with quotas if certain users have limited space allowance), multiple thin volumes will costs performance and administrative overhead
Prizm78
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Re: Does thin volume not auto expand when needed?

Post by Prizm78 »

dolbyman wrote: Tue Jul 27, 2021 12:27 am A thin volume is still limited to it's given size.

The allocation will grow when data is written to it, that's why they can be over-provisioned.
- So if i understand you correctly, if i create a thin volume and put it to 100GB, it is not allowed to go past that limit. Unless i resize and increase the volume?
- so basically if i set a thin volume to 100GB, but i have no data swimming inside it, it will not occupy any data from the storage pool until i start to upload files to that volume. To put it another way (if i may?), if i create a thin volume of 100GB, no data in it, it will not occupy any data from storage pool, if i upload a file of 26GB (*.MKV), then the thin volume will occupy data from storage pool and allows to do that all the way up to 100GB which is the limit i set, am i correct in my understanding?

Static is not really a question for me, then it has to be thick volume. but my "issue" as how i sees it is that i never know how much data i will put into every volume, it could be little it could be a lot.
The biggest volumes for me is where i keep my movie collection (converting my BlueRay collection) and where i have my virtual machine collection. Some of the dev-machines i have can take up A LOT of space. So being "stuck" with multiple thick/static is sort of giving less flexibility (at least i feel that way).

But of course i am always open to feedback and learn around this. :-)
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dolbyman
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Re: Does thin volume not auto expand when needed?

Post by dolbyman »

What you said about thin volumes was correct

You don't need to create separate volumes for similar storage types, you can device them by shares

Pool1 (spinning disks for mass storage)
-Volume1 (Thick)
--Share1 (e.g. Backups)
--Share2 (e.g. Movies)
--Share3 (e.g. etc)

Pool2 (SSD for high IOP usage)
-Volume1 (Thick)
--Share1 (e.g. VM Storage)
--Share2 (Database)

Adding Volumes instead of shares will slow everything down
dcolter
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Re: Does thin volume not auto expand when needed?

Post by dcolter »

@Dolbyman what is it about having multiple volumes that slows it down? Trying to understand what the overhead it creates is.
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dolbyman
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Re: Does thin volume not auto expand when needed?

Post by dolbyman »

This was about several thin volumes with snapshots (QNAP says that each volume with snapshots will impact the performance 5-30% on top of the lower performance of thin volumes anyways)
https://www.qnap.com/en-us/how-to/faq/a ... y-how-much
https://www.qnap.com/en/how-to/faq/arti ... ick-volume

I will close this due to necroposting .. please feel free to open a new thread if you offer to benchmark all sorts of scenarios (or want to hear what other people think)
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