Spotlight On: Solaris Volume Manager
 
Those of you involved in hardware maintenance have probably come across logical volumes at one time or another. In Solaris 8, Sun called it DiskSuite. In Solaris 9 and 10, Sun renamed it to Solaris Volume Manager (SVM). It's the same package, just a different name.
 
Logical volumes have been used for years on HP-UX and AIX. For any of you with experience on those platforms, the transition to SVM will be fairly simple, once you understand some of the terminology and concepts. For those of you that have used Sun's conventional hard partitions, SVM will take some understanding. This article will introduce SVM and explain SVM terminology. Learning SVM is much easier once you understand the terminology used.
 
Before the introduction of logical volumes, the system administrator was stuck with conventional hard slices. Each physical disk was limited to a maximum of 7 hard slices (0-7, not including slice 2). They are called hard slices because the slices are created by selecting actual physical cylinders from the disk. The slice starts at one cylinder and ends at another, and a slice cannot be larger than a single disk drive. A file system gets created on this slice. File systems can only span a single slice, therefore the size of a file system was limited to the total size of a disk. On the OS drive, hard slices get created when the OS is installed. If you run out of space, for example if /var fills up, it is difficult to resize the hard slice without destroying all of the data on the disk.