[Superorb]

What are the spec requirements of the cache drive? Does it need to be the same size as your biggest diskor can you use a smaller disk? I only had one 1tb 3GB/s sata drive connected when testing unraid and no cache disk but would you really need a cache disk for a one drive direct share? there should be no bottleneck to one disk. maybe ZFS is just faster...

The cache disk is used to speed up transfers to the server. You copy the files you want onto the server, and it will put them on the cache drive and bypass parity check for now. At a later time, a script will copy the files on the cache disk to the array at a slower rate since parity is calculated at that later time. Writes are just as slow when it does copy to the protected array, but it does so at 3am in the morning so you don't notice those slower writes.

When I first built my array I moved files to the server before assigning a parity drive, so all writes were not calculating parity. I was getting 90MB/s sustained. The parity calc is what slows down the writes.

With that said, I only get reads of 50MB/s when theoretically it should be the drive and gigE max since parity calcs are not done on reads. I don't know why reads are also slow. But, I never need to read that fast as even the beefiest BD rips are only 40mbps which 50MB/s is more than capable of sustaining.