"This article shows you how to boot from SAS storage (in this case, the IBM System Storage DS3200) using the IBM BladeCenter-H and x86-based BladeCenter HS21 and LS21 servers. (For BladeCenter-E, check the blade compatibility matrix listed below in the Resources section to see if your environment is supported.) You will also see how to enable multipathing in Linux. Multipathing, or multipath I/O, is a fault-tolerance and performance enhancement technique where more than one physical path exists between the CPU and its mass storage devices. Simple examples are a SCSI disk connected to two SCSI controllers on the same computer or a disk connected to two Fibre Channel ports.
"The major advantage of using external storage only is the improved availability of the server. Even though you can configure several different RAID levels using local disks within the blade only, you must shut down the system to replace a defective drive. Using external storage and hot-swap drives, you can replace defective drives without interrupting services. Recently, IBM announced blade servers, the BladeCenter HS12 and JS12 servers, with support for hot-swap SAS drives, but both are uniprocessor machines only."
