Our product save times were a disaster and our disks were being overloaded. I asked extendware what they thought because we already use their page cache product.
They told me it is due to tag deleting which causes a scan of the cache folder and said that performant cache backends would solve it. I installed it and immediately everything was faster and the problem has not returned! Product save times are half what they were and the disk is not being overloaded. Great!