Effectively using optical volume space

The usage of optical volume space is affected by the size of the objects and how the objects are written: chained by the storage management cycle or unchained by direct write to optical media. Table 1 provides an estimate of optical volume usage for media used with a operator-accessible optical drive.

Table 1. Effective optical volume usage for ibm optical disk media
Object size in KB	Effective utilization
Object size in KB	Data written by storage management cycle (chained)	Data written directly to optical volume (unchained)
40␠000	100%	93%
20␠000	100%	47%
10␠000	100%	23%
5␠000	100%	12%
4␠000	100%	9%
3␠000	84%	7%
2␠000	56%	5%
1␠000	28%	2%

Attention: In subsequent calculations, ensure that you use a value for the total number of cartridges required-per-day that is large enough to reflect your planned use of storage groups, multiple drives, and direct write to optical and or tape. The validity of those calculations depends on the accuracy of your total number of cartridges required-per-day estimate.

Related reading: For 3995 capacity information, see 3995 Introduction and Planning Guide.