[SOLVED] How to determine ARCsize?

[fireon]

Hello all,

i have here an server with ZFS an low memory (unfortunately not expandable). Memorysize is 32GB, Arcsize is 8GB. Can use even less here? For example 6GB, or less?

time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  arcsz     c 
19:47:14   329   104     31     0    0   104  100     0    0   8.0G  8.0G

 

[Tahsin]

That depends on your application and use case. One of my machines I have ARC size is set to 2GB max because most of the my drive activity are writes. Any reads I have are pretty static and my miss% is only 10. It may not be a clear advice but you can definitely try reducing it and see if you notice any performance hit. Worst case scenario, you will be reading from your drive instead of ram thus the performance hit depending on your drive type.

 

[fireon]

Very thanks, this helps

 

[guletz]

Hi,

You can also increase the RAM allocated for your VM and setup for them using:

primarycache=metadata

In a such case, you will not double cache the same data(at arc level and at vm cache level). Guest know better than zfs what data to cache or not.

Good luck / Bafta.

 

[fireon]

Good thing you mentioned that, I've already set that for backups. I am now also trying in the pool. Since data are only in VM's, and not in separate datasets.

 

[fireon]

Looks good. With 5GB and on some Volumes and Datasets ein set primarycache=metadata.