3590 is the machine type of a tape backup system based on the 1/2-inch cartridge which uses a linear serpentine recording technique.
"Effective September 29, 2006, IBM will withdraw from marketing the 3590 Enterprise Tape Drive. The IBM TotalStorage 3590 Enterprise Tape Drive has been replaced by the IBM System Storage TS1120 Tape Drive." 
There are several models of 3590s: standalone single drive, rackmounted with autoloader, etc.
The alpha character following the dash indicates what kind of read/write drive is used.
- 3590-B drive
- 128 tracks
- V3R2 and later
- 3590-E drive
- 256 tracks
- V4R1 and later
- 3590-H drive
- 384 tracks
- V4R5 and later
There are two kinds of 3590 media, distinguishable by the color of the plastic insert on the cartridge and the single letter designation.
- 3590-J media
- blue tab
- 1050 feet
- 3590-J tapes can be referred to as "3590" or "native" tapes, as they were the original length.
- 3590-K media
- green tab
- 2070 feet
- 3590-K tapes can be referred to as "3590E" tapes, as they are the "extended" length. This has nothing to do with the 3590-E drive model.
The capacity of a given 3590 cartridge depends on the drive, the media, and compression.
It varies from 10GB to 180GB per cartridge.
- Note: (##GB) denotes capacity with compression.
- (PDF) of IBM Magstar 3590 Tape Subsystem
- Document Number: GA32-0330-05
- Build Date: May 1999
3590 Reference Codes
- Tape Drive Model Characteristics table from IBM Reference# 8625688700566393
- Differences between 3590 Model B , E, and H Tape Drives from IBM Reference# 862569C1006571B1
- (PDF) of IBM TotalStorage 3590 Tape Drive datasheet from IBM
- 3590 info from IBM Tivoli Storage Manager, Version 5.3 for AIX Server
- Imation links
- Imation Black Watch 3590 & 3590E 1/2" Data Cartridges
- (PDF) of Imation 3590/3590E Half-Inch Tape Cartridge Brochure
- (PDF) of IBM TotalStorage data sheet for media and drives (G325-3369-20) from IBM
- wikipedia:Magnetic tape
- Identifying computer tapes with images from Disc Interchange Service Company
- http://www.ribeau.co.uk/guest/3590%20Magstar%20Tape%20Subsystem/ has PDFs of IBM manuals and other documents