My current server runs FreeNAS, which I have booting from mirrored 40 gig Intel SSDs.  I dead-set on moving over to UnRAID and I won't need these drives for boot purposes anymore.  Would two 40 gig SSD drives be useful for cache drive purposes or is that not enough space to bother in UnRAID?  I have five 5TB drives and eight 2TB drives.  I plan to buy one more 5TB drive (or 6TB) and run everything with dual parity, slowly replacing all the drives with 6TB drives.  But the drive upgrade process will be slow going for sure.  It's all hooked through a dual Xeon setup with 64 gigs of ECC ram.  Probably overkill for UnRaid but it was all very useful in FreeNAS.  Regardless it's time for me to ditch that scene and UnRAID is where I'm headed.  So, I'm wondering if I should bother doing anything with the SSDs or just remove them from the system.  Thanks for the help.

They may be useful if you plan to use dockers or VMs, for caching data they are small and also 40GB SSDs usually have a low sequential writing speed, likely slower than a modern HDD.

Unraid will use that ram! it uses cache drives and ram for temporary files. I only have 24gb of ram and it says that about 18 gigs is reserved for cached data. 

Thanks.  They are Intel 320 series drives.  So yes, the speeds are not  great.  https://ark.intel.com/products/56568/Intel-SSD-320-Series-40GB-2_5in-SATA-3Gbs-25nm-MLC  But do plan on using Docker and VMs.  I guess I'll figure out something to do with these old drives that's not caching related.  

3 minutes ago, jonny6pak said:

I guess I'll figure out something to do with these old drives that's not caching related.

You can still use them to make a cache pool for the dockers/VMs, just don't enable cache for the media shares so unRAID writes straight to the array.

Ahh I get it now. Thanks for the insight.