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Double Tape Recording Techniques (Data Security Mode, Performance Mode)

IP.com Disclosure Number: IPCOM000014345D
Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Abstract

This article describes a new method for reading and writing data onto a tape. Target of this method is to approach the current requirements for using tapes as data storage. The method is based on a double tape cartridge (one cartridge with two independant tapes in it) in accordance with a double tape drive (a tape drive with two independant tape pathes in it). Using this technology it is possible to implement innovative recording modes.

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Double Tape Recording Techniques (Data Security Mode, Performance Mode)

     This article describes a new method for reading and writing data onto a tape. Target of this method is to approach the current requirements for using tapes as data storage. The method is based on a double tape cartridge (one cartridge with two independant tapes in it) in accordance with a double tape drive (a tape drive with two independant tape pathes in it). Using this technology it is possible to implement innovative recording modes.

     Tapes are historically seen the common media to store and archieve data. The requirements for tapes are as follows:

     Customers applications (especially HSM applications) need a high data rate to satisfy the users requirements. High data rates can only be achieved by fast tape motion and sophisticated recording technology. Compared to DASD tapes are considered to be cheaper. Also customers do not want to loose data.

     The more space the customer can store on a single tape the less room is needed for equipment. Also the overhead to manage the data is decreasing if more data fits on a single tape. Last not least the space requirements customers have to store the data is increasing.

     The customer's focus is usually to a subset of the mentioned requirements. There are customers which have the focus in regard to read/writeperformance. The objective of those customers is to have a fast tape subsystem which records the data in high speed and does not do as much recovery in case of a recording problem. Other customers focus is to store data very secure. Those customers usually manage multiple copies of the same datasets (Insurances, Banking Trusts). Performance is not the major focus in those environments.

The double tape technology constists of two parts:

1. A tape cartridge with two seperated tapes and tape wheels in it - refered to as double tape cartridge.
2. A tape drive which constists of two seperated tape pathes (loading mechanism, read write mechanism, incl. read write buffer and logic) and one common channel controller. The common channel controller is the central control mechanism of the double tape drive and the interface to the attached computer system. The double tape drive appears like one tape drive externally (for the attched computer system). Internally it consists of two tape paths.

     When the double tape cartridge is loaded into the double tape drive one tape is loaded into tape path1, the other into tape path 2. It may be necessary to load just one tape into the double tape drives' path1, path 2 may not be loaded.

     Every of the two tape in the double tape cartridge is considered to be one independant tape by the double tape drive channel controller. The channel controller ensures that the information written on the two tapes in the double tape cartridge is consistent. For that it may be necessary to implement a header control information for every tape. The channel controller may be responsible for the header information a...