![]() ![]() The concatenated LEs do not have to be contiguous. Striped LVs allocate each successive LE from a different PV depending on the size of the LE, this can improve performance on large sequential reads by bringing to bear the combined read-throughput of multiple PVs.Īdministrators can grow LVs (by concatenating more LEs) or shrink them (by returning LEs to the pool). Systems can use LVs as raw block devices just like disk partitions: creating mountable file systems on them, or using them as swap storage. The pooled LEs can then be concatenated together into virtual disk partitions called logical volumes or LVs. The system pools LEs into a volume group (VG). PVGs are usually laid out so that they reside on different disks or data buses for maximum redundancy. These PEs are drawn from a physical volume group (PVG), a set of same-sized PVs which act similarly to hard disks in a RAID1 array. With mirroring, multiple PEs map to each LE. ![]() Normally, PEs simply map one-to-one to logical extents (LEs). Some volume managers (such as that in HP-UX and Linux) have PEs of a uniform size others (such as that in Veritas) have variably-sized PEs that can be split and merged at will. Volume management treats each PV as being composed of a sequence of chunks called physical extents (PEs). They start with physical volumes (PVs), which can be either hard disks, hard disk partitions, or Logical Unit Numbers (LUNs) of an external storage device. If LVM sounds like something that you are interested in or is something you are looking to get started with, I have written a few articles to discuss the basics and configuration of each piece of the LVM puzzle.Most volume-manager implementations share the same basic design. From here, we can create various types of logical volumes (LV) to suit our needs using the lvcreate command. The volume group takes on the full capacity of the combined devices and is seen as a single storage device. Once you have your physical volumes, we can combine those into a single volume group (VG) using the vgcreate command. These are physical "block devices" that must be initialized for LVM use, using the pvcreate command. At the heart of LVM, your physical volumes (PV) will act as your starting point. In the past, you would have to unmount the volume in order to change its properties however, LVM only requires this when downsizing. This means that a sysadmin can allocate more space for a volume on the fly. So, what advantages does it offer? Well, the big thing for most people is that LVM allows for dynamic resizing. LVM was written in 1998 and has been a powerful ally for sysadmins since that time. Logical Volume Manager (LVM) doesn't completely alleviate these concerns however, it is a bit more forgiving if you make an error in your calculations or just decide to do something different in the future. Historically, this would involve a lot of pre-planning and precision. Cheat sheet: Old Linux commands and their modern replacementsĭisk management has always been one of the most important tasks that system administrators perform.Linux system administration skills assessment.A guide to installing applications on Linux.Download RHEL 9 at no charge through the Red Hat Developer program. ![]()
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