This chapter describes the GFS volume manager — named Pool — and its commands. The chapter consists of the following sections:
Pool is a GFS software subsystem that presents physical storage devices (such as disks or RAID arrays) as logical volumes to GFS cluster nodes. Pool can aggregate storage devices either by concatenating the underlying storage or by striping the storage using RAID 0. Pool is a cluster-wide volume manager, presenting logical volumes to each GFS node as if the storage were attached directly to each node. Because Pool is a cluster-wide volume manager, changes made to a volume by one GFS node are visible to all other GFS nodes in a cluster.
Pool is a dynamically loadable kernel module, pool.o. When pool.o is loaded, it gets registered as a Linux kernel block-device driver. Before pool devices can be used, this driver module must be loaded into the kernel. (Once the driver module is loaded, the pool_assemble command can be run to activate pools.)
Pool includes a set of user commands that can be executed to configure and manage specific pool devices. Those commands are summarized in the next section.
More advanced, special-purpose features of the Pool volume manager are described later in this chapter.