I'm not an expert of SANs, I'm writing here to get some clues on continuous and exasperating problems we're having which our supplier seems not to be able to solve.
we own an ENHANCE ES3160P4 SAN with 16 x 2 Tb disks that has been supplied for our video surveillance system. The SAN has been configured by the supplier to use 14 disks within a RAID 5 array, and 2 disks are global spares. The RAID is usually divided into 2 virtual disks of equal size that span across the whole RAID space. Each one results to be something more than 12 Tb. Each virtual disk corresponds to a single LUN, that is attached to a single video server which continuously stores video data and allows users to retrieve recordings when needed. The LUNs are formatted with NTFS and are attached to Windows Server 2012 videoservers through iSCSI. The videoservers tend to fully use the available space they have.
With this configuration the disks of the SAN are failing and failing, and each time the SAN cannot recover the RAID because another disk fails in the meanwhile. We lost the RAID like 4 times in the last few months.
This problem seems not to be caused by a bad SAN sample, because we own other three machines of the same type similarly configured that seem to have the same problems. Only one has no problems, but at the moment it's underused.
After some months of unknown tests and checks, the supplier ended up saying that it's well-known that the SAN should not be used 100% or it will degrade fast, also physically, and said that to solve the problem the virtual disks should be created leaving a 10-15% of the total space available in the RAID.
I searched the web for the problem, and didn't find specific statements saying this. It seems to me that it would be more reasonable to create virtual disks spanning the whole RAID and then underuse the LUNs (that is, allowing Windows to have free space and avoid fragmentation). If not, I don't understand why the ENHANCE SAN allows to create virtual disks that span the whole RAID if it's so "well-known" that some free space must be left, and why the supplier configured the system like this at the beginning...but that's another point.
In the end, we want to solve this situation. Any suggestion is accepted. As said, I'm not a SAN expert, but after so many problems I'd like to really understand whether the supplier knows what is going on or not, because we cannot accept this situation anymore.
Many thanks in advance! Regards
Edit: disk type As from the answer it seems to be relevant information, I add that the disks are all Western Digital model WD2001FYYG-01SL3.