U.2 SLC SSD as cache?

[miniwalks]

Hey guys,
I have access to some Dell/Micron 350GB NVMe U2 drives and was wondering what they'd be like as cache disks?

Cheers


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[m0nkey_]

What sort of cache are we talking, SLOG or L2ARC?

The question you should be asking yourself is, do you really need either SLOG or L2ARC?

FreeNAS likes RAM, the more you add the better the system will perform. If you're thinking L2ARC, max out your RAM and watch your ARC stats/ratio, that will tell you if you need an L2ARC. An L2ARC will also utilize RAM, which is why you should max it out first. If you're doing synchronous writes, such as a NFS datastore for ESXi then use it as a SLOG to improve write performance. If you're not doing this, then a SLOG is going to do nothing to improve performance.

Adding a 'cache' device for the hell of it can be detrimental to your systems performance.

 

[miniwalks]

Sorry, should have specified, these will be for SLOG cache as the Array is destined to be a nfs store for an esxi cluster


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[SweetAndLow]

What is that disks endurance rating? Needs to be super good.

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[miniwalks]

Lifetime endurance is 25PB according to tech sheets

MTBF is 2mil device hours, which is 228.3years @24x7

25PB into 228.3 years is 109.5TB per day, 4.5TB per hour.