Currently (by 2015/March) the only Qsan NAS model that supports FC connections is U300-F30.
Because upgrades from U300-P10 to U300-F30, the iSCSI feature will be disable. U300 can't support iSCSI and FC pcotocols at the same time.
A RAID disk can be replaced only with a free disk in the system. If a disk is already set to spare disk then the replacement using that disk is controlled by the system and you cannot use it to manually replace any RAID disks. For doing so you'll have to first set the disk to free status by clicking on the set free disk icon, and then select the disk options from the target RAID disk to be replaced manually.
On Qsan NAS only blocks with data need to be rebuild upon any disk replacement. The more data you have in the pool, the longer it takes to rebuild. Besides, try to avoid frequent user accesses to the storage during reb uilding process as the more I/O interference during rebuilding (from running data services), the slower the rebuilding speed could be.
All Qsan NAS with 12 bays or more have full support to SSD cache feature.
Considering system stability, we would only recommend SSD disk models listed in the compatibility matrix to be used. However, any unapproved SSD cache drives could also be used in this case as long as they can be detected and recongnized by the system. As the contents stored on SSD cache drives are only cached data, the original dataset would not be impacted upon any SSD cache drive mulfunction events, though performance would then be dropped down to the status without SSD cache drives in the worst case.
The Qsan NAS products support up to 6 SSD cache drives (4 read and 2 write) for every pool created in the system.
No, each SSD drive can only be assigned as SSD cache disk for one pool.
The SSD write cache on Qsan NAS is only useful for improving Sync write access. If it's all Async writes performed to the pool, then the overall performance would not benefit much from the SSD write cache usage. For more details please refer to the SSD cache deployment application note from Qsan partner portal.
On Qsan NAS the compression algorithm works based on LZJB algorithm natively provided in ZFS.