Any point to SSDs as cache/log in my use case?

TrueNAS General
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1

My TrueNAS server is mostly used for Plex, file storage, and file backups.

I’ve got a 256 GB SSD and a 512 GB SSD sitting around unused from builds/upgrades of friend’s PCs and I’m wondering if trying to use them as cache/log/etc is going to actually produce any benefit.

I know that TrueNAS has options for drives being used for cache/log/metadata/etc VDEVs, but I’m curious if using either the 256 or 512 SSDs in those kinds of VDEVs will actually reduce file read or write times.

I’ve got four 8TB HDDs in a RAIDZ1 config inside the TruenNAS PC.
I use two 128GB 2.5" SSDs mirrored for app storage.
AMD Ryzen 3100 + X570 board 48GB DDR4 RAM
TruenNAS PC connects to the rest of the network on a 10G connection

Thanks!

If I’ve left out necessary info, let me know and I’ll add that ASAP.

2

Your use case (as specified) does not indicate any use for a SLOG device.

I doubt that an L2ARC would help, but you can check that by looking at the output from arc_summary (possibly sudo arc_summary).

I have

ARC total accesses:                                                11.9G
        Total hits:                                    99.3 %      11.8G
        Total I/O hits:                               < 0.1 %       1.2M
        Total misses:                                   0.6 %      77.1M

Which says that with a 99.3% hit rate, an L2ARC will be a waste

3

No.

4

The performance of SSDs vary greatly. If those are typical consumer SSDs, then I would guess that even if your workload could benefit from a SLOG/L2ARC/special vdev/etc. using those SSDs for such may even hurt your performance.

Before deploying any device, especially an SSD, as an accelerator or any type, run performance benchmarks against the device you are thinking of using. Make sure the benchmark reflects the load the device will see.

The other thing to do is benchmark your pool performance before adding the accelerator and again after to see if you did help the situation (or hurt it).