摘要:
Provided are a computer program product, system, and method for generating a code alphabet for use by a deployed program to determine codewords for words. A first code alphabet is generated having a first number of symbols that provide variable length codings of the words. The symbols in the first code alphabet are merged into a second number of groups of the symbols in the first code alphabet, where the second number is less than the first number. A second code alphabet is generated having the second number of symbols, wherein a second average codeword length of the codewords produced using the symbols in the second code alphabet is smaller than the codeword length (b) of the words, and wherein the second code alphabet comprises the code alphabet used by the deployed program.
摘要:
Provided are a computer program product, system, method, and data structure for using variable length code tables to compress an input data stream to a compressed output data stream. A determination is made as to whether a number of at least two consecutive data units in the input data stream match the number of consecutive data units in a history buffer of previously received data units in the input data stream. If so, a copy pointer symbol is generated including data indicating a copy pointer symbol referencing previously received data units in the history buffer and indicating the determined number of consecutive data units. A determination is made of a relative displacement count in the history buffer at which the number of matching consecutive data units start. A determination is made from a variable length code table an encoding of the relative displacement count in the history buffer.
摘要:
According to one embodiment, a method includes storing instances of a file in a first storage tier and a second storage tier of a storage system; associating each instance of the file on the first and second storage tier with a unique program identifier (UPI); receiving a request to access the file or instance thereof from a user in a group of users; searching for a UPI associated with an instance of the file that exists on the first storage tier; and providing the user requesting access to the file with remote access to the instance of the file on the first storage tier. Additional methods are also presented.
摘要:
A method, system and program are provided for enabling selective access to multiple users' encrypted data in a single storage cartridge. A unique, derived key is generated for each user's data by performing cryptographic operations on a combination of a common base key and metadata related to the data to be encrypted (e.g. its total block count). The base data key is wrapped with one or more encryption keys to form one or more encryption encapsulated data keys (EEDKs). The base key and the derived key are wrapped to create a session encrypted data key (SEDK), which along with the EEDKs, are conveyed to the tape drive, where the SEDK is decrypted. The EEDKs are then stored in one or more places on the storage cartridge. The base key and the derived key are used to encrypt a predetermined user's data, with the derived key stored on the cartridge with the encrypted data. The encrypted data may be subsequently decrypted by retrieving the EEDK and decrypting it with a decryption key to extract the base data key. The extracted base data key can then be used with other information to calculate the derived key. Once calculated, the derived key is used to decrypt its associated encrypted data.
摘要:
A method, system, and machine-readable medium for controlling access to data of a tape data storage medium are disclosed. In accordance with one embodiment, a method is provided which comprises conveying data access control metadata from a tape cartridge comprising a tape data storage medium to a host, receiving decrypted metadata from the host, comparing a checksum value determined utilizing the decrypted metadata with checksum data stored within the tape cartridge; and processing a request to access the tape data storage medium received from the host based upon a comparison of the checksum value and checksum data. In the described method embodiment, the data access control metadata comprises encrypted metadata corresponding to a data storage parameter, where data is stored within the tape data storage medium utilizing the data storage parameter and the decrypted metadata is generated by the host utilizing the encrypted metadata.
摘要:
A method, system, and machine-readable medium for controlling access to data of a tape data storage medium are disclosed. In accordance with one embodiment, a method is provided which comprises conveying data access control metadata from a tape cartridge comprising a tape data storage medium to a host, receiving decrypted metadata from the host, comparing a checksum value determined utilizing the decrypted metadata with checksum data stored within the tape cartridge; and processing a request to access the tape data storage medium received from the host based upon a comparison of the checksum value and checksum data. In the described method embodiment, the data access control metadata comprises encrypted metadata corresponding to a data storage parameter, where data is stored within the tape data storage medium utilizing the data storage parameter and the decrypted metadata is generated by the host utilizing the encrypted metadata.
摘要:
A method, system and program are provided for enabling access to encrypted data in a storage cartridge by wrapping the data key used to encrypt the data with one or more encryption keys (e.g., a public key from a public/private key pair) to form one or more encryption encapsulated data keys (EEDKs) and then storing the EEDK(s) on the storage cartridge along with the encrypted data. The encrypted data may be decoded by retrieving the EEDK from the storage cartridge, decrypting the EEDK with a decryption key (e.g., the private key from the public/private key pair) to extract the underlying data key, and then using the extracted data key to decrypt the encrypted data.
摘要:
A write-once read-many (WORM) optical disk recorder automatically calibrates its laser to emit a laser beam of a desired power level. While writing data to the WORM disk, a laser test signal is written to a laser checking area termed Automatic Laser Power Correction (ALPC) field. If the emitted laser test signal has a power level outside an acceptable power level window, then inappropriate laser power is indicated. Then, in an error recovery procedure (ERP) the laser power is calibrated in the data sector to be written to using short spaced-apart laser test signals. After successful calibration, data are written to the sector. The test signals appear as burst errors that can be corrected by a suitable error correction code. If such calibration is not successful then a write calibrate sector, WCS, is created and used for an extensive automatic calibration. In the WCS both laser power level is calibrated. The calibration result information is written to WCS for later use. A WCS may be created by command from a controller or attaching host for calibrating the laser and its control circuits in a WORM disk device. The WCS can also be written as a part of an ERP initiated by an unsuccessful write operation in one or more target sectors. Such initiation is based upon a determination that an inappropriate write power level may have been used in the attempted data writing.
摘要:
A record carrier having essentially circular tracks concentrically located around a point of rotation. The record carrier is divided into circular zones each having m tracks, where m is an integer. Each track within a zone is subdivided into n sectors, where n is an integer which is constant per zone and which increases as the zone is more remote from the point of rotation. Each sector including a header portion and a data portion. The header portions in the radial direction in each zone are in line. In each zone the condition of m*n=j*k is satisfied, where is j an integer greater than or equal to 2 and is constant for each zone, and k is an integer.
摘要:
A drive circuit for a laser which has the capability of eliminating transient conditions when switching a high frequency modulator on or off, and including elements for maintaining desired depth of modulation. These capabilities are included in a circuit that automatically compensates for changing conditions due to temperature, laser characteristics and fluctuations in media reflectivity.