Hi I am pretty much an OpenBSD / FreeNAS noob, but I'm on my 4th or 5th server rebuild since my first try summer 2014. This is a home server, no "crown jewels" in the data.
I have a question about my setup and why my ZFS Hit ratio is so low.
I started with NAS4Free and then, when I had problems getting some jails up and running, migrated to FreeNAS.
Somewhere along the line I decide that the old repurposed machine I was using wasn't cutting it and bought a dedicated server. It made all the difference, and I couldn't be happier.
Anyway, I have a Lenovo TS140 server with an i3-4130 @ 3.4GHz. I have 20 GByte of DDR3 ECC RAM
I have two pools.
The one called CFS_Media is a stripe of 3 disks - one 2-TByte WD Blue HD and two 500-GByte Maxtor drives. No redundancy because the data is not critical - just a bunch of music, movies, TV series, etc.
The second pool is called CFS and has all my family's important files. It is simply a mirror of two 1-GByte that I backup externally once a week.
This pool also houses all my jails -- plex, couchpotato, owncloud, transmission, and two minecraft servers for my boys. Only couchpotato and transmission are plugin jails. The others manually installed.
So from what I can tell, my server functions perfectly. God I love Plex! Owncloud gives me peace of mind as I've got it set up to sync all of our user files from all of my family's accounts across all of our 4 computers.
I know you are not supposed to use owncloud as part of a backup strategy, but I think it works for our laptops and desktops in case of hard drive failure on one of those... and if one of my kids opens up an email with CryptoLocker virus or something - i've at least got my weekly backups.
Anyway, I digress... my problem is that all over this forum, people say that my ZFS ARC hit ratio should be between 90 and 100%, yet mine is not. Also, the best I can tell, my server never uses any swap but always reserves 10 GByte RAM for it.
Despite my server apparently functioning perfectly, you all would say that it is not. But for what I'm doing, 20 GByte of DDR3 ECC RAM should be enough I would think.
Below are my numbers. Can someone with more knowledge about this help me figure out if there is anything I can optimize?
[*]Put your data type(s) here...
[*]86.0GiB / 928GiB (CFS)
[*]794GiB / 2.71TiB (CFS_Media)
[*]943MiB / 14.9GiB (freenas-boot)
[*]2.23GiB (MRU: 9.09GiB, MFU: 9.09GiB) / 20.00GiB
[*]Hit ratio -> 81.14% (higher is better)
[*]Prefetch -> 2.34% (higher is better)
[*]Hit MFU:MRU -> 96.89%:0.87% (higher ratio is better)
[*]Hit MRU Ghost -> 0.00% (lower is better)
[*]Hit MFU Ghost -> 0.00% (lower is better)