Hewlett-packard Company

Crossroads Systems, Inc.

Kip Cr P1 LP

Bradfred W Culp

Stephen G Dale

Terry L Loseke

Kevin S Saldanha

Allen J Piepho

Alfred Natrasevschi

An intermediate device communicatively connected to a host device and a sequential device in a storage area network. The host device is configured to issue different kinds of commands to the sequential device, including an inquiry command. The sequential device is configured to sequentially process requests from the host device. The intermediate device is configured to cache inquiry data about the sequential device itself in a cache memory connected to the intermediate device and service inquiry commands from the host device.

System and method for caching inquiry data about sequential access devices

A system and method for servicing an inquiry command from a host device requesting inquiry data about a sequential device on a storage area network. The inquiry data may be cached by a circuitry coupled to the host device and the sequential device. The circuitry may reside in a router. In some embodiments, depending upon whether the sequential device is available to process the inquiry command, the circuitry may forward the inquiry command to the sequential device or process the inquiry command itself, utilizing a cached version of the inquiry data. The cached version may include information indicating that the sequential device is not available. In some embodiments, regardless whether the sequential device is available, the circuitry may process the inquiry command and return the inquiry data from a cache memory.

System and method for inquiry caching in a storage area network

A system and method for servicing inquiry commands, wherein inquiry data is stored in a memory and if an inquiry command for a target device is received while the target device is busy processing another command, the stored inquiry data is returned in response to the command. In one embodiment, a router contains a memory for storing static inquiry data corresponding to each of a plurality of sequential devices connected thereto. The first time a host sends an inquiry command to one of the sequential devices, the router routes the command to the target device and stores the data returned by the device. Subsequent inquiry commands are serviced by passing the command through to the target device if it is not busy, or returning inquiry data from the router's memory if the target device is busy processing another command.

Inquiry data received from sequential target devices is stored in a cache memory. In one embodiment, the cache memory is coupled to a router. In one embodiment, when the router receives from a host an inquiry command about a target, the router first checks to see if the inquiry command can be serviced from the cache. If so, the inquiry data about the target is retrieved from the cache and returned to the host. If not, the router checks to see if the target is busy. If not busy, the router routes the inquiry command to the target and stores the inquiry data returned by the target in the cache. If the target is busy, the router places the inquiry command in a queue. When the target becomes available, the router forwards the inquiry command to the target for processing, thereby keeping the inquiry command from timing out.

System and method for servicing inquiry commands about target devices in storage area network

A system and method for servicing inquiry commands, wherein inquiry data is stored in a memory and if an inquiry command for the target device is received while the target device is busy processing another command, the stored inquiry data is returned in response to the command. In one embodiment, a router contains a memory for storing static inquiry data corresponding to each of a plurality of sequential devices connected thereto. The first time a host sends an inquiry command to one of the sequential devices, the router routes the command to the target device and stores the data returned by the device. Subsequent inquiry commands are serviced by passing the command through to the target device if it is not busy, or returning inquiry data from the router's memory if the target device is busy processing another command.

System and method for inquiry caching

Disclosed is a system that stores write management information identifying which sectors have been written and which sectors are available to be written in a magneto-optical disk with write-once-read-many (WORM) capability. The write management information is stored in a separate write management directory on the media, which is typically loaded into the drive controller memory when the media is first loaded into the drive. Whenever the drive receives a write command, it checks the write management directory to determine if the sector has already been written. If the directory indicates that the sector has already been written, the drive returns an error, otherwise, the drive writes the sector and updates the write management directory. In the preferred embodiment, two separate methods are used to indicate that a sector has been written.

Method for using one of two storage directories only after the other

Block pattern detection circuitry for the read subsystem of a streaming tape drive system comprises a state machine, a pattern decoder, a tape mark detector, a block/gap filter, a block/gap meter, a verify count section, and a block read/verify section. The incorporation of a hardware state machine within the block detect circuitry permits the application of historical detect data in the interpretation of present detect data. This provides more certain pattern recognitions. Also, state data is fed back to the block/gap filter allowing precise block boundary triggers which are used by position capture circuitry and the drive controller to effect more precise re-try positioning. The use of the block/gap filter increases the detect circuitry's immunity to noise. The advantage is enhanced where the block/gap filter uses stochastic thresholding, which is also advantageously employed by the tape mark detector.

Block pattern detection circuitry

A tape driven system includes means for capturing data block boundaries while moving in reverse, as well as in the forward direction. Thus, block boundaries can be captured following each reversal of tape direction to cancel prior errors induced during tape reversals provided these errors are within tolerance. In a hitch operation, the rear boundary of a data block is recaptured as a reference position for the next forward operation. In a backspace operation, the front boundary of a data block is captured while the tape is moving in the reverse direction to provide a reference point for the next operation.

Growing community of inventors

Greeley, CO, United States of America

Bradfred W Culp