I would like to know if there is any problem (e.g. wear out faster, performance will degrade fast, as TRIM isn't supported, ...) if I use Hybrid HDD (e.g. SATA3 2.0TB SEAGATE SSHD HYBRID 64M ST2000DX001) on ReadyNAS Ultra 2 (the price is not a problem).
SSHD drives are mechanical drives with a large (8 GB) cache, so TRIM isn't relevant. Whether that cache helps performance much depends on the workload (random I/O on a small working set probably would be faster, since performance would be disk-bound, not network bound).
I haven't seen any test results of SSHDs in RAID-5 or RAID-6 though.
Also, the mechanical drive mechanism of the ST2000DX001 is believed similar to the DM drives, which don't seem to fare that well in NAS RAID arrays. So personally I wouldn't use them.
I am not relay looking for performance gain, but more for reliability, since SSHD use less the mechanical (headers). The most used files are hold on the cash side (SSD). I have also used ST2000DM001 in RAID for a few years without any problem. Since the price is almost the same (HD vs SSHD) I would like to use SSHD. Actually the question is: can SSHD be worse than HD on ReadyNAS Ultra 2 ?
I don't think they will perform worse than the ST2000DM001s. Not sure about reliability (or whether your thinking about less wear will turn out to be true in practice).
In a larger NAS there could be issues due to vibration,but I don't see that as a problem on the Ultra-1.
These are just guesses though, since no one using these disks replied.
