Media types¶
Description¶
CTA will manage over 30000 tapes made up of 6 different media types. CTA stores the following attributes about each media type:
- Media type name.
- Cartridge.
- Capacity.
- Primary tape density SCSI code.
- Secondary tape density SCSI code.
- Number of wraps on the tape.
- Minimum longitudinal position.
- Maximum longitudinal position.
The media type name is a human readable name chosen by operators to best describe the unique type of a tape in a short and concise manner. Examples could be LTO8-12TB or 3593JD-15T. The cartridge attribute is used by operators to identify the physical type of a tape. Examples include LTO7 and 3592JD. End users write to pool of tapes which can be made up of different media types. The capacity attribute is used by CTA to calculate the total capacity of each of these tape pools. The SCSI tape density codes are a machine readable specification of a tape’s density. These codes will be used by CTA to ensure tapes are only mounted into drives which support reading and/or writing their specific density. Data is stored on tapes in a serpentine layout made up of several wraps. A single wrap travels the entire length of a tape. The total number of wraps on a tape together with the minimum and maximum longitudinal positions of the tape will be used by CTA to read back files in an efficient order when the tape drive technology being used does not support Recommended Access Order (RAO).
Mapping between the CASTOR tape density and the CTA catalogue schema¶
In order to facilitate the migration of metadata from CASTOR to CTA it was necessary to specify which columns of the CASTOR VMGR_TAPE_INFO and VMGR_TAPE_SIDE tables map to which columns of the CTA catalogue MEDIA_TYPE table.
| VMGR Densities | CTA Media Type |
|---|---|
| 7000GC | 3592JC |
| 8000GC | 3592JC |
| 9TC | LTO-7M |
| 10TC | 3592JD |
| 12TC | LTO-8 |
| 15TC | 3592JD |
Table 7 on page 20 of the following tape drive manual list tape capacities, densities and cartridges: