Hello.   You should have attempted to clear the foreign configuration on the drives.   It is not normally advisable to power down the system while the RAID array is in a degraded state and drives in a foreign configuration.   First try booting into the RAID controller BIOS and see whether you can be able to import the existing foreign configuration in order to recover your data. You may try to recreate the array with original parameters but there is no guarantee that you will recover the data given the foreign status of some drives; and if you did so it may be corrupted.
Howdy.  I have a T720 with a PERC H810 configured as follows.  All drives are SATA in an external (custom made) enclosure.  With two SFF-8088 cables wired into the drives. As such you cannot blink a light on a drive for ID. RAID 1 (OS): 2x 1TB SATA Drives  RAID 6 (DATA): 6x 6TB SATA Drives (WD Reds)  I check this server every month for drive failures.  The RAID 1 has no critical data.  The RAID 6 is not critical, but painful to recreate the data that is on it so I would like to save it. Yesterday, a drive started making noise.  Sounded like bearings or head crash.  omreport storage vdisk showed that the RAID 1 was 'degraded' -and- the RAID 6 had 'degraded redundancy'.  Checking physical disk status showed however that poth 1TB drives were fine, and that one drive in the RAID 6 had failed.  This seemed unusual given that both vdisks were in a degraded state.  While I have plenty of extra 1TB drives on hand I did not have a spare 6TB.  I had Amazon overnight an identical 6TB. This morning I open the drive enclosure to identify the screecher.  It was one of the 1 TB drives in the RAID 1.  Getting more confusing as pdisk status still showed no failed 1T drives. I decided to rebuild the RAID 1 first, so I swapped that drive for a new 1TB.  When I went into the PERC setup and looked at the foreign config it showed two drives as foreign, the new 1TB and one of the 6TBs (which were all original, none swapped yet).  The RAID 6 also showed a missing member.  My gut says it was just the bad drive having lost the on disk config and it showing as foreign, but I wanted to investigate.  I powered down and checked serial numbers, did not move any cabling, other than to check seating. On repower the RAID controller has lost all config.  "All drives from your previous configuration are gone." I think I am pretty well hosed here.  I am considering trying to recreate the arrays (without initializing) to get data, but given that there were questionable drives (but still enough redundancy), I do not know if that is the right tactic to take. If anyone has other ideas, please let me know.  Thanks a bundle.
Kaboom goes the RAID