Arrays are not a problem in general - they normally have internally, redundant
batteries to hold up the cache.
The issue is when you have an internal hardware RAID card with a large cache.
Those cards sit in your server and the batteries on the card protect its
internal cache, but do not have the capacity to hold up the drives behind it.
Normally, those drives should have their write cache disabled, but sometimes
(especially with S-ATA disks) this is not done.