I just installed a new Storage Server 2012 R2 OEM box, with a single mirrored storage space using 4x Samsung 840 Pro SSDs and 12x 3TB Toshiba 7200RPM HDDs. I used the wizard to configure this as a tiered space with a single large virtual drive, and it appears to have configured with 2 columns and a 1GB writeback cache on the SSDs, as well as a proper tiering scheme between the SSDs and HDDs.
The scheduled task starts tiering maintenance at 10pm (I moved it back from 1am), and tiering runs all night with 100% disk activity at very low throughput (0.5 - 3.0 MBps), until I stop the Storage Spaces Tiering service in the AM when users arrive, as they report bad storage response times while it runs - very little data is added to the disk during the day (say, 5 - 10GB), and usage patterns don't change much, so I'm curious as to why this is happening.
I've let the service run a few times over weekends, and it sometimes "finishes" a run, but the next night it will go right back to churning at low throughput and continue into the morning until a manual service stop.
Any ideas?