Hi,

 

I'm planning a build and I have an OCZ Agility 2 120GB SSD hanging around. I was planning that as a cache - as I'm unlikely to need more than 120gb of cache on a normal day. However what concerns me is what if I have a need to copy a large bulk for files? Say 200GB. Do I get the 120gb of speed benefit then the remaining 80gb at array write speeds?

 

Thanks

 

Hi,

 

I'm planning a build and I have an OCZ Agility 2 120GB SSD hanging around. I was planning that as a cache - as I'm unlikely to need more than 120gb of cache on a normal day. However what concerns me is what if I have a need to copy a large bulk for files? Say 200GB. Do I get the 120gb of speed benefit then the remaining 80gb at array write speeds?

Yes in principle although it is important you set the cache Minimum Free space value to get the desired behaviour.

 

What you need to do is set Settings->Global Share Settings->Cache Settings->Min. Free Space value for the cache drive to be larger than the largest file you will write.  Then when the free space on the cache drive falls below this level unRAID will write further files directly to the array drives by-passing the cache (until mover runs and the Free Space gets above the minimum value you have set).  The reason this is important is that if you do not set it unRAID may select the cache drive for a file, and then run out of space writing the file.  In such a scenario you get an error on the write (i.e. unRAID does not dynamically switch that particular file to an array drive) and the copy fails.