How much RAM is needed for a ZFS mirroring layout on TrueNAS SCALE ?

[vn_mnm]

Hello everyone,

I am planning to build my own NAS device running TrueNAS SCALE with 1 x 128GB SSD (OS drive) & 2 x 16TB HDDs in a ZFS mirroring layout similar to RAID 1. At minimum, how much RAM do I need to install on my motherboard ?

Thank you very much in advance.

 

[NugentS]

And what is your use case?

 

[sretalla]

At minimum, how much RAM do I need to install on my motherboard ?

Depending on what you expect it to do, the minimum is 8GB.

With 16TB of capacity, you might be happier with performance with 16GB of RAM... again depending on the workload you're throwing at it.

If you're just sharing files over SMB and playing media with Plex or Emby, 16GB is probably enough. 32GB may not deliver enough additional performance to notice unless you have a different, more demanding workload.

 

[NugentS]

I use a TN with 8GB, as a backup device - getting snapshots sent to it overnight. Not sure I would want to server files from it - but for its purpose it fine.

 

[vn_mnm]

And what is your use case?

Thanks for your comment. I will be mainly using this as a file server hosting raw photo files from my cameras. However, it is a nature of ZFS filesystem to demand an additional of 1GB of RAM for every 1TB of HDD added into the pool, thus this topic comes into being.

So, if I am to install 2 x 16TB HDDs, will I have to install 32GB of RAM on the motherboard ? Or is 16GB enough in a ZFS mirroring layout similar to RAID 1 ?

 

[NugentS]

Do you intend to edit the files from the NAS or just store them? How big are individual files (in general)?
The 1GB for 1TB is a generalization. 8GB is minimum, I would use 16 and keep options open (if you can) for 32

 

[vn_mnm]

Do you intend to edit the files from the NAS or just store them? How big are individual files (in general)?
The 1GB for 1TB is a generalization. 8GB is minimum, I would use 16 and keep options open (if you can) for 32

I plan to use my NAS mainly for storing the photos. The catalogue of the files as well as editing will be on my personal desktop PC.
Regarding the files, at the moment, since I am shooting with an APS-C digital camera, each of its raw files is on average 50MB, and the Photos folder on my PC now has almost reached 100GB. In the forseeable future, I plan to purchase another Medium Format digital camera and the APS-C system will be relegated to informal, travelling photography. From my Google research, each of the Medium Format’s raw file will be approximately 230MB on average. So 2x 16TB HDDs seem to be future proof for me.

If so, how much would you recommend me on the RAM size !?

 

[vn_mnm]

Depending on what you expect it to do, the minimum is 8GB.

With 16TB of capacity, you might be happier with performance with 16GB of RAM... again depending on the workload you're throwing at it.

If you're just sharing files over SMB and playing media with Plex or Emby, 16GB is probably enough. 32GB may not deliver enough additional performance to notice unless you have a different, more demanding workload.

Thank you for your comment. It is actually the ZFS requirement of 1gb of additional RAM for every marginal increase of 1tb in HDD drive pool that worries me. In my case of just using 2x 16TB HDDs for a ZFS mirroring layout similar to RAID 1, are 32 gigs of RAM still needed !?

 

[sretalla]

If so, how much would you recommend me on the RAM size !?

16GB would allow you to cache about 8GB (maybe as much as 10GB) in ARC.

That's about 10% of all your photos at this point, so I would say it's plenty.

 

[vn_mnm]

16GB would allow you to cache about 8GB (maybe as much as 10GB) in ARC.

That's about 10% of all your photos at this point, so I would say it's plenty.

So, for a ZFS mirroring layout using 2 x 16TB HDDs, how much RAM would you eventually recommend ? 16 or 32 gigs ?

 

[sretalla]

So, for a ZFS mirroring layout using 2 x 16TB HDDs, how much RAM would you eventually recommend ? 16 or 32 gigs ?

I already voted and stated above that 16GB is probably fine assuming you only do photo storage and access and you're not accessing the whole library in full all the time.

 

[vn_mnm]

I already voted and stated above that 16GB is probably fine assuming you only do photo storage and access and you're not accessing the whole library in full all the time.

Thanks for your advice. However, a part of my brain still screams for 32GB of RAM. Does 32gb in my case make any realistic performance gain or just psychological assurance ?

 

[sretalla]

Does 32gb in my case make any realistic performance gain or just psychological assurance ?

I doubt you would be able to tell the difference except in the most extreme of circumstances, when you're transferring a substantial part of your library (but not more than about 20GB), twice in a row (where only the second run would be "better").

Waste your money if it makes you sleep better.