Abstract: Methods, systems, and products for delayed deletion of extended attributes associated with a file in a file system are provided. Embodiments include identifying a file to delete, moving an extended attribute directory associated with the file to a background deletion directory, deleting the file, and deleting in the background the extended attribute directory. Some embodiments also include deleting an ACL associated with the file.

Abstract: An apparatus, system, and method are disclosed for differential data backup using snapshot on-write data. A snapshot module maintains an on-write data structure that captures a point-in-time or temporal instance of a data set by tracking modifications to data blocks of a data set. A backup module copies the data set to a backup data storage device as a full data set backup. In addition, the backup module copies each modified data block indicated by the on-write data structure and a differential time stamp to the backup data storage device as a differential data set backup. The full data set backup and one or more differential data set backups form a plurality of temporal instances of the data set. In one embodiment, a restore module recovers a selected instance of the data set responsive to receiving a restore command by copying the full data set backup to a target data storage device.

Abstract: A method for calibrating a laser transmitter includes (a) detecting an eye diagram of an output from the laser transmitter, (b) determining if the eye diagram is acceptable, (c) if the eye diagram is not acceptable, changing a value of a control signal in the laser transmitter, wherein the control signal sets an amplitude characteristic of a limiting amplifier coupled to a laser driver in the laser transmitter, and (d) repeating steps (a), (b), and (c) until the eye diagram is acceptable.

Abstract: An apparatus and method for distributing work on a doubly linked list to a plurality of worker threads are provided. With the apparatus and method, an initial thread obtains the list lock for the linked list and inserts a marker element at the beginning of the linked list. Elements in the linked list that are before the marker element in the linked list are considered work that has been assigned or work that has been completed. Elements of the linked list that are after the marker element in the linked list are work to be done. The initial thread spawns worker threads to perform the work on the linked list and passes the address of the marker element to each of the worker threads. Each worker thread then operates independently to perform work on the linked list based on the current position of the marker element in the linked list.

Abstract: A serialization detection arrangement determines whether a received IO request requires serialization. An overlap detection arrangement then determines if the received IO request produces an impermissible overlap condition. Each IO request producing an impermissible overlap condition is blocked so that it cannot be executed by a storage device while the impermissible overlap condition exists. However, IO requests avoiding an impermissible overlap condition are passed on to the storage device to be executed at the device. Blocking or passing IO requests is preferably performed by an IO request control arrangement. Upon receipt of an IO done signal for a particular IO request, a completion arrangement starts any IO request that had been blocked by the particular IO request and updates the records for both pending requests requiring serialization and blocked IO requests.

Abstract: A spin transistor having wide ON/OFF operation margin and producing less noise is provided. The spin transistor includes a substrate having a channel, a source, a drain and a gate formed on the substrate. The source and the drain are formed to have magnetization directions perpendicular to the length direction of the channel. The ON/OFF operations of the spin transistor can be controlled by generating a spin-orbit coupling induced magnetic field to have a direction parallel or anti-parallel to the magnetization directions of the source and the drain.

Abstract: A laser transmitter includes an input stage generating an input signal to a limiting amplifier, the limiting amplifier generating an input signal to a laser driver, and the laser driver generating an input signal to a light source. The limiting amplifier has a control terminal for receiving a control signal that sets an amplitude characteristic of the input signal to the laser driver. The amplitude characteristic may be a common-mode or a peak amplitude of the input signal to the laser driver.

Abstract: A system and method in a data processing system for recovering data in a file system. A request to modify a data block in the file system is detected. In response to detecting the request to modify the data block, metadata describing the data block in the file system is written in a log. In response to detecting an error during the writing of the metadata, an error counter is incremented. Finally, in response to a request to recover the data in the file system, the metadata is read only if the error counter is less than or equal to a predetermined value.

Abstract: An apparatus, system, and method are disclosed for differential data backup using snapshot on-write data. A snapshot module maintains an on-write data structure that captures a point-in-time or temporal instance of a data set by tracking modifications to data blocks of a data set. A backup module copies the data set to a backup data storage device as a full data set backup. In addition, the backup module copies each modified data block indicated by the on-write data structure and a differential time stamp to the backup data storage device as a differential data set backup. The full data set backup and one or more differential data set backups form a plurality of temporal instances of the data set. In one embodiment, a restore module recovers a selected instance of the data set responsive to receiving a restore command by copying the full data set backup to a target data storage device.

Abstract: A method, apparatus, and computer instructions for managing data in a file system in a data processing system. A request to modify a data block in the file system is detected during file system recovery time. In response to detecting the request, metadata is written to describe the data block into a snapshot image. The data is copied for the data block in the file system to the snapshot image. The data block is modified in the file system after the data is copied into the snapshot image. The snapshot image may be used to return the file system to a state prior to modifying the data block in the file system.

Abstract: A method and apparatus for ensuring valid journaled file system metadata during a backup operation are provided. With the method and apparatus, mechanisms are provided for suspending write I/O operations to storage devices during a point-in-time backup operation. Once the point-in-time backup operation is completed, the suspended write I/O operations are released and may then be processed by the storage system. In one exemplary embodiment, when a point-in-time operation is initiated, a point-in-time backup flag is set in a logical volume manager. In response to receiving a write I/O operation, the logical volume manager checks the status of the point-in-time backup flag to determine if a point-in-time backup operation is currently being performed. If the flag is not set, then the write I/O operation is logged and performed in a normal manner. If the flag is set, then the write I/O operation is stored in a hold queue of the logical volume manager.

Abstract: An extended attribute data page includes extended attribute information about a number of files. The page is divided into areas, each area corresponding to a different file. A given area is further divided into a number of lines containing information about the extended attribute data. Areas include bitmaps indicating available space in the data space and address information for addressing off-page data areas. A directory is included of data types stored in the data area, and additional lines store extended attribute data. The extended attribute directory maintains a list of data types currently stored and related information. Including availability information about each line along with addresses to areas storing extended attribute data enables the extended attribute manager to efficiently determine where to place extended attribute data, mark deleted lines as being available, retrieve data being requested by a process, and modify the contents of a given extended attribute data type.

Abstract: A 3 group-5 group compound ferromagnetic semiconductor, comprising one material ‘A’ selected from the group of Ga, Al and In and one material ‘B’ selected from the group consisting of N and P, wherein one material ‘C’ selected from the group consisting of Mn, Mg, Co, Fe, Ni, Cr and V is doped as a material for substituting the material ‘A’, the compound semiconductor has a single phase as a whole. The ferromagnetic semiconductor can be fabricated by a plasma-enhance molecular beam epitaxy growing method and since it shows the ferromagnetic characteristics at a room temperature, it can be applied as various spin electron devices.

Abstract: A method and apparatus for a multiple concurrent writer file system are provided. With the method and apparatus, the metadata of a file includes a read lock, a write lock and a concurrent writer flag. If the concurrent writer flag is set, the file allows for multiple writers. That is, multiple processes may write to the same block of data within the file at approximately the same time as long as they are not changing the allocation of the block of data, i.e. either allocating the block, deallocating the block of data, or changing the size of the block of data. Multiple writers is facilitated by allowing processes performing write operations that do not require or result in a change to the allocation of data blocks in a file to use the read lock of a file rather than the write lock of the file. Software serialization or integrity mechanisms may be used to govern the manner by which these concurrent write operations have their results reflected in the file structure.

Abstract: An extended attribute data page includes extended attribute information about a number of files. The page is divided into areas, each area corresponding to a different file. A given area is further divided into a number of lines containing information about the extended attribute data. Areas include bitmaps indicating available space in the data space and address information for addressing off-page data areas. A directory is included of data types stored in the data area, and additional lines store extended attribute data. The extended attribute directory maintains a list of data types currently stored and related information. Including availability information about each line along with addresses to areas storing extended attribute data enables the extended attribute manager to efficiently determine where to place extended attribute data, mark deleted lines as being available, retrieve data being requested by a process, and modify the contents of a given extended attribute data type.

Abstract: A mechanism is provided for maintaining quota information in extended attributes associated with a quota data file. A quota data file includes file control information, including attributes such as a file name. The quota data file control information includes a reference to an extended attributes directory. Each user record is stored as an extended attribute in the extended attributes directory. Each extended attribute also has file control data. The quota information for a user is stored in-line in the file control data.

Abstract: An apparatus and method for distributing work on a doubly linked list to a plurality of worker threads are provided. With the apparatus and method, an initial thread obtains the list lock for the linked list and inserts a marker element at the beginning of the linked list. Elements in the linked list that are before the marker element in the linked list are considered work that has been assigned or work that has been completed. Elements of the linked list that are after the marker element in the linked list are work to be done. The initial thread spawns worker threads to perform the work on the linked list and passes the address of the marker element to each of the worker threads. Each worker thread then operates independently to perform work on the linked list based on the current position of the marker element in the linked list.

Abstract: A file system maintains information about files in data areas called dinodes. Dinodes are grouped into dinode pages wherein each dinode page includes information about one or more dinodes. Each dinode may use extended attribute data. Each dinode page having at least one dinode that uses extended attribute data has a corresponding dinodex page. The dinodex page includes extended attribute information about any of the dinodes in the dinode page that use extended attribute information. The page is divided into areas, each area corresponding to a different dinode. A lock is established for each dinode page so that any dinode adding or deleting its extended attribute address obtains the lock before proceeding to maintain cooperation between the dinodes. In this manner multiple extended attribute areas are prevented from corresponding with a particular dinode page and unused extended attribute pages are removed without unduly impacting system performance.

Abstract: A system and method for releasing storage space at the beginning of a byte stream while maintaining sequential byte stream semantics is provided. A ghost offset is initialized when a file is instantiated or opened. When information is deleted at the beginning of the sequential byte stream, the ghost offset is incremented in the amount of the number of bytes being deleted. The ghost offset continues to increment while the file is opened and information is being deleted at the beginning of the data stream. The virtual offset is the ghost offset added to the real offset of a particular entry in the data stream which maintains sequential byte stream semantics. When the file is closed, storage space is released in the amount of the ghost offset. Applications are provided with virtual offsets corresponding to data locations which are converted to real offsets for accessing data in the data stream.

Abstract: A serialization detection arrangement determines whether a received IO request requires serialization. An overlap detection arrangement then determines if the received IO request produces an impermissible overlap condition. Each IO request producing an impermissible overlap condition is blocked so that it cannot be executed by a storage device while the impermissible overlap condition exists. However, IO requests avoiding an impermissible overlap condition are passed on to the storage device to be executed at the device. Blocking or passing IO requests is preferably performed by an IO request control arrangement. Upon receipt of an IO done signal for a particular IO request, a completion arrangement starts any IO request that had been blocked by the particular IO request and updates the records for both pending requests requiring serialization and blocked IO requests.