I use TrueNAS to store weekly backups and other data for my systems at home, no VMs or other apps.
Last time I transferred a 700GB system backup from another PC, I noticed the available RAM in my server’s GUI was dwindling to almost nothing, then stopped the transfer.
I’m using 8x 4TB drives in a single pool as RAID-Z3, and currently have 64GB of RAM installed.
I’m also considering adding another identical pool or two for added redundancy in the future, will that require even more RAM?
That’s normal–your system has the RAM, so ZFS ought to use it. For your pool, 64 GB are enough. More is likely to be better, but check your ARC stats in the Reporting pages. But you don’t need more RAM based on what you’ve described.
So I could benefit from more? How much more would be ideal?
My motherboard can take up to 256GB.
Maybe. What do your ARC statistics look like?
The likelihood that you can benefit significantly with 64 GB of RAM and 20 TB of usable pool capacity is pretty small. But, again, TrueNAS has instrumentation to help you out here.
What makes you think, as you’ve titled the thread, that you need to increase your RAM?
I restarted the transfer and the ARC seems to be holding steady at 57GB, and there’s 2-3GB not being used.
I was afraid the ARC would take more and run out.
Still, would the system be happier if I added more RAM?
I guess, because if OP had called the thread “should I increase my RAM for ZFS” he would’ve triggered @winnielinnie
I guess, but probably not measurably. For the third time, what do your ARC statistics look like?
I don’t think your system would operate much different with more RAM if your measure is writing a single large file.
Let me toss in a wrench… why is the ARC filling up so quickly? You are not able to write data faster than your current pool layout.
If there is a transfer rate issue, fix the pool layout.
Honestly, it sounds like your system is running fine. It will not run out of RAM because if the system needs more RAM, it will take some back that it loaned to the ARC.
The transfer rate averages 200MB/s when writing to the pool.
Do you think that can be improved?
That is absolutely what it is supposed to look like. What would you suggest the system do with that RAM instead?
Unused RAM is wasted RAM. If you add e.g. VMs to your configuration they will get their configured share of your physical memory but the ARC will always fill up the rest sooner or later. That is the point of a cache.
All RAM which is not used by anything different will be used as cache. In any modern operating system.
HTH,
Patrick
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I wasn’t aware that the RAM would be freed-up as needed when I made this thread.
If I don’t need more RAM, I’ll keep the funds.
