Creating a Hot Sparewww.3ware.com 135Creating a Hot SpareYou can designate an available drive as a hot spare. If a redundant unitdegrades and a hot spare the size of the degraded disk (or larger) is available,the hot spare will automatically replace the failed drive in the unit withoutuser intervention. When this occurs, an event notification is generated andappears in the list of alarms in 3DM.It’s a good idea to create a hot spare after you create a redundant unit.In order to replace a failed drive, a hot spare must have the same or largerstorage capacity than the drives it is replacing.For 9550SX controllers, the Auto-Rebuild policy allows automatic rebuildingto occur with drives that are not designated as spares. For more information,see “Setting the Auto-Rebuild Policy” on page 123.Note: 3ware’s 9000 series RAID controllers use drive coercion sothat drives from differing manufacturers and with slightly differentcapacities are more likely to be able to be used as spares for eachother. Drive coercion slightly decreases the usable capacity of adrive that is used in redundant units.The capacity used for each drive is rounded down to the nearestGB for drives under 45 GB (45,000,000,000), and rounded down tothe nearest 5 GBytes for drives over 45 GB. For example, a 44.3GB drive will be rounded down to 44 GBytes, and a 123 GB driveswill be rounded down to 120 GBytes.If you have 120 GB drives from different manufacturers, chancesare that the capacity varies slightly. For example, one drive mightbe 122 GB, and the other 123 GB, even though both are sold andmarketed as “120 GB drives”. 3ware drive coercion uses the samecapacity for both of these drives so that one could replace the other.Specifying a Hot Spare through 3DMIf you need to add a drive to be used as the hot spare, follow the instructionsunder “Adding a Drive through 3DM” on page 160.To specify a hot spare after the system is booted1 In the Available Drives section of the Maintenance Page, select the driveby checking the box next to it.2 Click Create Unit.3 In the dialog box that appears, select the configuration type Spare.4 Click Ok.You will see the spare appear at the top of the page, under UnitMaintenance.
