VAST enables you to impose quotas on directories in the Element Store.
A quota (can) limit the amount of storage and/or the number of files/objects that can be contained in the directory. Writes are blocked when hard limits are reached, while soft limits can be defined at lower levels for warning purposes. It's also possible to define a grace period to limit how long you allow the soft capacity limit to be exceeded.
Limitations apply to moving directories in and out of quota-controlled directories. The following moves are not supported:
Moving a directory between two quota-controlled directories.
Moving a directory out of a quota-controlled directory into a directory that is not controlled by a quota.
Moving a directory from a directory that is not controlled by a quota into a quota-controlled directory.
There is no limitation on moving files from one directory to another.
Quota capacity usage is counted according to used bytes in each file and not according to the logical file size. Bytes are counted in blocks of 32KB. A file that is smaller than 32KB is counted as taking 32KB of quota space.
A file with 8KB of data (contiguous offsets 0-8k) would consume 32KB of quota capacity. 10,000 such files would consume 320,000KB=~320MB of quota capacity although they comprise only 80MB of logical data.
Although the files would be counted as using 32KB of quota capacity they would use no more than 8KB of SSD space (less with compression/deduplication).
Many operating systems support sparse files, which are files that are allocated disk space only for the used bytes and not for the empty bytes in the file. The logical file size can be much larger than the allocated space taken by the file. VAST Cluster is aware of sparse files and does not count the empty bytes in a sparse file as quota capacity. For example, a sparse file whose logical file size is 500GB but only 64MB were written to it uses only 64MB of quota capacity.
When a directory's soft limit is reached, the alarm "SOFT_EXCEEDED" is triggered.
If the directory remains in excess of the soft limit for the time defined as the grace period, an additional alarm, "GRACE_EXPIRED," is triggered and the directory is blocked to writes.
If the directory reaches the hard limit, the alarm "HARD_EXCEEDED" is triggered, and the directory is blocked to writes.