recommended minimum performance for log devices

[truenasinterested]

Hello,
i have a
NVMe 1.3/PCIe 3.0 x4 SSD (1TB) (via CPU lanes)
NVMe 1.3/PCIe 3.0 x1 SSD (1TB) (via PCH lanes but not much happening there)

I doubt that i will have much benefit of using any of those (as far as i tested) but of course, you can always continue to test and maybe they are able to offload access times in my rotational drive array for logs.

Anyhow, i only want to do non-impacting logs for data security (i.e. L2ARC and Cache VDEV).
The x1 SSD obviously is limited in performance (approx. 1GB/s).
What do you recommend: which drive for what? I'd use the x4 for cache and the x1 for L2ARC.

 

[ChrisRJ]

I recommend that you provide detailed information about your hardware and use-case. How can we help without those?

 

[Etorix]

Anyhow, i only want to do non-impacting logs for data security (i.e. L2ARC and Cache VDEV).
The x1 SSD obviously is limited in performance (approx. 1GB/s).
What do you recommend: which drive for what? I'd use the x4 for cache and the x1 for L2ARC.

Additionally I recommend that you do more reading about ZFS. The links in @ChrisRJ 's signature would be a good start.
L2ARC is indeed a read "cache", but how could it "help with data security"?
SLOG is NOT a cache, and is only of use with synchronous writes, which you may or may not have. Assuming your workload does require sync writes and could do with a SLOG, the minimal requirements are: Power-Loss Protection (i.e. no consumer-grade drive!), high endurance and low write latency.

 

[truenasinterested]

you're right, sorry and i will immediately forget the SLOG - i am using SMBv3 mostly.
The aim is a 10Gbe filer for general purpose storage + Plex. Hardware in the below.

Show : System

Asrock Rack E3C246D4U2-2L2T
64GB DDR3 2400 ECC
Crucial MX500 256GB SATA System drive
10x Toshiba MG10ACA in RAIDZ2
Broadcom 9400-16i
StarTech PCIe adapter card for 2 NVMe 1.3 SSDs (with Broadcom bridge)
ConnectX3

I guess then the question is already done as the x4 SSD is already in use for L2ARC.

 

[Patrick M. Hausen]

Monitor your ARC and L2ARC usage with arcstat. If you have an ARC hit rate of 99% or higher, your L2ARC does not do much good, either. You could even profit from removing it, because that frees RAM that is currently used to manage the L2ARC.