SFS Overview › Allocation of Space in User Storage Groups

Allocation of Space in User Storage Groups

An SFS administrator can specify an allocation limit for each user storage group in any file pool known to CA VM:Secure. The allocation limit is the amount of storage that all SFS managers can allocate from a particular user storage group, and is normally greater than the physical amount of storage.

For instance, you can set the allocation limit of a user storage group to 100 percent. This means that SFS managers can allocate the space in this user storage group up to its physical size. If the size is 10,000 blocks, then SFS managers can allocate 10,000 blocks of its space. However, you can also set the allocation limit of a user storage group to 500 percent. In this case, SFS managers can allocate the space in this user storage group up to five times its physical size; if the size is 10,000 blocks, then SFS managers can allocate 50,000 blocks of space.

Allocation of a user storage group beyond its physical size allows for the most efficient use of space on your system. It is similar to the practice of overbooking airline flights: not everyone with an airline reservation shows up for the flight, so that reserving several more seats than actually exist on a plane increases the chances that the flight will be as full as possible. Similarly, not every user ID with an allocation in a user storage group uses its full amount of space, so that allocating more space than actually exists in a user storage group increases the chances that the space will be used as fully as possible.

You can allow a user storage group to be allocated by any percentage of the physical amount of space, from 100 percent to 9999 percent, where 100 percent means that the space can be allocated only to its physical size.

Because this allocation limit is a percentage of the user storage group’s physical size, you can increase the size of a user storage group without having to adjust this allocation limit. For instance, if you allow 200 percent allocation for a user storage group that has 10,000 blocks, that storage group has 20,000 blocks of effectively allocable space. If you later increase the physical size of this storage group to 25,000 blocks, its effectively allocable space becomes 50,000 blocks.