VXA is a tape backup format originally created by Ecrix and now owned by Tandberg Data. After the merger between Ecrix and Exabyte on 17 November 2001, VXA was produced by Exabyte Corporation. On November 20, 2006, Exabyte was purchased by Tandberg Data that has since stopped further development of the format.Phone call with Tandberg technical support, speaking to a former Exabyte engineer on July 2, 2010.
Operation Exabyte and Ecrix describe the data format as "packet technology."Exabyte whitepaper describing VXA Packet Technology Since VXA is based on helical scan technology, data is written across the tape from side to side in helical strips.
The novel part of VXA packet technology is that each stripe starts with a unique packet ID and ends with an ECC packet checksum. As each stripe is written to tape, it is immediately read back to verify that the write was successful.
If the write was not 100% successful the packet can be rewritten at another point on the tape without stopping. When the data is read back, the packets are reassembled into a "buffer" by their packet ID.Another VXA Packets explanation The buffer has 3 additional ECCs to ensure data integrity.
Another aspect of VXA is that there are 2 read heads for each stripe, slightly offset in relation to each other to allow for more flexibility in reading tapes written by other drives.
Due to the relatively slow tape speed inherent to helical scan technology, the drive is able to stop and start the tape much more quickly to avoid the need to backhitch.
Market context The VXA format competes mainly against the DDS,Exabyte's DDS to VXA migration sales pitch and DLT-IVExabyte's DLT to VXA migration sales pitch formats.
Overview Generation VXA-1 VXA-2 VXA-3 VXA-4 VXA-5 Release date 1999 2002 2005 Unreleased Unreleased Max native (uncompressed) capacity (GB) 33 80 160 320 640 Max speed (MB/s) 3 6 12 24 48 Encoding EFM PRML Track width 9.1 μm 5.7 μm Head Ferrite TFMR
VXA-3 Exabyte released two different product lines based on VXA-3 technology, VXA-320 in 2005 and VXA-172 in 2006. VXA-172 drives are limited to 86 GB per tape cartridge, but can be unlocked (for a fee) to remove the limit. They are otherwise the same. VXA-3 was the first helical scan system in production to feature thin film MR heads.
Notes Data Capacity figures above are for uncompressed data. Exabyte assumes a 2x compression factor in their marketing material.
Media Media was released on two families (V and X), with different capacities based on the length of the tape, and the drive it is being used in.
Product V6 V10 V17 V23 X6 X10 X23 Length (Meters) 62m 107m 170m 230m 62m 124m 230m Native Capacity (when used in the given type of drive - empty means not compatible) VXA-1 12 GB 20 GB 33 GB VXA-2 20 GB 40 GB 60 GB 80 GB 20 GB 40 GB 80 GB VXA-172 40 GB 86 GB VXA-320 160 GB 40 GB 86 GB 160 GB
Gallery
Cartridge / tape
Mechanism / drive
Tape and drive together
References
External links
ECMA 316 Specification of VXA-1. ECMA 222 Specification of ALDC, the data compression standard for VXA-1. VXA Alliance