Question re Cache for media server

TrueNAS General
1

I use my trunas as a Media Server. Once it starts a file it will read & serve it to the end. It should serve the files fast, but if it dies, it can restore from backup, which is acceptable. It doen’t need to cache the most recetly used files, if anything these are the files least likley to be accessed. Strangley down time is “ok” but slowness is not. it’s 99% a read system, write speed is almost irrelevant, it’s reads that count.

I have 12 spindle disks set as 8 in 1 pool (36TB) 83% used, 4 in 1 pool (50TB) 73% used, my zfs cache is reporting 32GB, I’m about to upgrade it to 64GB. I think that should be enough to cache the entire file(s) But should I add a NVME ssd, running on a PCIE card to use as L2ARC cache? I currenty have a spare 500gb sata SSD on the controller that would have to be removed to make space for the NVME controller.

What would you advise?

Thanks

2

go to shell and take a look at arc_summary, specifically the arc hit ratio. If it’s above 90% you don’t need an l2arc.

3

Thanks for that. I’ll have a look :slight_smile:

My server only turns on at 18:00 and off at 01:30, would it remember the stats? I can leaveit on for a few days if it needs to be

In the UK the costs of electricity went through the roof, hence it’s only on when needed.

4

ARC is reset after reboot so you are fighting a losing battle in this regard Im afraid to say. With you on UK energy costs.

5

It’s been running this morning, rather unusualy, and the arc stats are, I think good. No need for l2arc, I think
"
ARC totak accesses (hits and Misses) 25.5m
Cache hit ratio 98.4% 25.1M
Actual hit ratio (MFU + MRU) 87.1% 22.2m
"