ZFS is notorious for it's RAM requirements. The "rule of thumb" for ZFS is 1GB of RAM per TB of storage. My question is, does anyone know if BTRFS falls under a similar rule? I've been googling around and can't seem to find anything that gives a conclusive answer. Though that's probably me and PEBKAC when it comes to googling.
ZFS / BTRFS RAM requirements...
- Thread starter OhEsEcks
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Man of Honour
I'n yet to come across any solid info either.
ZFS will happily run with under 1GB/1TB but you won't see the full benefits of the ARC and ZIL caches.
What sort of workload will the system see. I've ran my NAS as low as 2GB RAM on 5TB storage and saw no difference in transfer speeds over Gigabit Ethernet.
Benching the pool however I'm sure the story would be different
ZFS will happily run with under 1GB/1TB but you won't see the full benefits of the ARC and ZIL caches.
What sort of workload will the system see. I've ran my NAS as low as 2GB RAM on 5TB storage and saw no difference in transfer speeds over Gigabit Ethernet.
Benching the pool however I'm sure the story would be different
Workload will be storage for my media collection mostly (films, music, digitising my pictures from negatives / scanning old images), backup system for machines around the house, that sort of thing.
But I have 16x2TB disks. So by FreeNAS ROT, I'd need 32GB of RAM for the storage alone. Which makes choosing hardware a pain in the ass since Celerons and E3 Xeons support a max of 32GB. I'd need to go E5 (something like E5-2603v2) to support more than 32GB of RAM, or older (second hand) Opteron / Xeons to keep the cost down.
If BTRFS requires less RAM it would save people a lot when it comes to RAM'ing up their systems.
But I have 16x2TB disks. So by FreeNAS ROT, I'd need 32GB of RAM for the storage alone. Which makes choosing hardware a pain in the ass since Celerons and E3 Xeons support a max of 32GB. I'd need to go E5 (something like E5-2603v2) to support more than 32GB of RAM, or older (second hand) Opteron / Xeons to keep the cost down.
If BTRFS requires less RAM it would save people a lot when it comes to RAM'ing up their systems.
Man of Honour
16 or 32GB for the entire system low would suffice.
As I mentioned earlier I ran my ZFS Virtual Machine as low as 2GB ram on 5TB storage and could still saturate gigabit
As I mentioned earlier I ran my ZFS Virtual Machine as low as 2GB ram on 5TB storage and could still saturate gigabit
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This. I've done the same thing, even running it within a virtual machine and got sustained transfer rates of >110MB/s. It will be fine for your usage.
The stuff i read recently on the FreeNAS forums was stating not that high RAM capacity was required for speed, but required for data integrity. In fact, reading about trying to run a 5Tb NAS with 4Gb (FreeNAS have 8Gb as a min) scared me so much I didn't bother doing it!