34 Storage Controller Features• Battery and optional Non-Volatile Cache backup of controller cache toprotect data• Detection of batteries with low charge after boot upThe next sections describe some methods to achieve fault tolerance.Using Persistent Hot Spare SlotsThe H700 and H800 cards can be configured so that system backplane orstorage enclosure disk slots are dedicated as hot spare slots. This feature canbe enabled using the Dell OpenManage storage management application.Once enabled, any slots with hot spares configured automatically becomepersistent hot spare slots. If a hot spare disk fails or is removed, a replacementdisk that is inserted into the same slot automatically becomes a hot spare withthe same properties as the one it is replacing. If the replacement disk does notmatch the disk protocol and technology, it does not become a hot spare.NOTE: Any hot spares assigned to an encrypted Virtual Disk must also be capableof encryption (SED).Physical Disk Hot SwappingHot swapping is the manual replacement of a disk while the H700 and H800cards are online and performing their normal functions.The following requirements must be met before hot swapping a physical disk:• The system backplane or enclosure must support hot swapping for thePERC H700 and H800 cards to support hot swapping.• The replacement disk must be of the same protocol and disk technology.For example, only a SAS hard drive can replace a SAS hard drive; only aSATA SSD can replace a SATA SSD.• The replacement disk must be of equal or greater capacity than the oneit is replacing.Failed Physical Disk DetectionFailed physical disks are detected and rebuilds automatically start to newdisks that are inserted into the same slot. Automatic rebuilds can also happentransparently with hot spares. If you have configured hot spares, thecontrollers automatically try to use them to rebuild failed physical disks.
