Abstract: Example apparatus and methods reserve space in a journal using an observation based approach instead of a fixed sized approach or a worst case scenario approach. One example method receives a request to allocate space in a journal to support a file system transaction. The example method reserves an amount of space in the journal based on a pre-existing reservation size estimate. Unlike conventional systems, the estimate is not based on a worst-case scenario. The example method observes the actual amount of storage used in the journal by the file system transaction and then selectively automatically adjusts the pre-existing reservation size estimate. The estimate may slowly shrink if no overflows are encountered but may quickly grow if an overflow is detected.

Abstract: Example apparatus and methods reserve space in a journal using an observation based approach instead of a fixed sized approach or a worst case scenario approach. One example method receives a request to allocate space in a journal to support a file system transaction. The example method reserves an amount of space in the journal based on a pre-existing reservation size estimate. Unlike conventional systems, the estimate is not based on a worst-case scenario. The example method observes the actual amount of storage used in the journal by the file system transaction and then selectively automatically adjusts the pre-existing reservation size estimate. The estimate may slowly shrink if no overflows are encountered but may quickly grow if an overflow is detected.

Abstract: Example apparatus and methods reserve space in a journal using an observation based approach instead of a fixed sized approach or a worst case scenario approach. One example method receives a request to allocate space in a journal to support a file system transaction. The example method reserves an amount of space in the journal based on a pre-existing reservation size estimate. Unlike conventional systems, the estimate is not based on a worst-case scenario. The example method observes the actual amount of storage used in the journal by the file system transaction and then selectively automatically adjusts the pre-existing reservation size estimate. The estimate may slowly shrink if no overflows are encountered but may quickly grow if an overflow is detected.

Abstract: Example apparatus and methods reserve space in a journal using an observation based approach instead of a fixed sized approach or a worst case scenario approach. One example method receives a request to allocate space in a journal to support a file system transaction. The example method reserves an amount of space in the journal based on a pre-existing reservation size estimate. Unlike conventional systems, the estimate is not based on a worst-case scenario. The example method observes the actual amount of storage used in the journal by the file system transaction and then selectively automatically adjusts the pre-existing reservation size estimate. The estimate may slowly shrink if no overflows are encountered but may quickly grow if an overflow is detected.

Abstract: Example apparatus and methods reserve space in a journal using an observation based approach instead of a fixed sized approach or a worst case scenario approach. One example method receives a request to allocate space in a journal to support a file system transaction. The example method reserves an amount of space in the journal based on a pre-existing reservation size estimate. Unlike conventional systems, the estimate is not based on a worst-case scenario. The example method observes the actual amount of storage used in the journal by the file system transaction and then selectively automatically adjusts the pre-existing reservation size estimate. The estimate may slowly shrink if no overflows are encountered but may quickly grow if an overflow is detected.

Abstract: Apparatus, methods, and other embodiments associated with reducing metadata controller communication volume are described. One example apparatus produces tracking data by tracking metadata controller communications and then controls which of two different types of metadata controller communication message types are used for metadata controller communications based, at least in part, on the tracking data. One message type provides actual state and/or location information about a metadata controller. A second message type provides only information about the state and/or location information available at a metadata controller. Selectively using the second message type facilitates reducing metadata controller communication volume.

Abstract: Example apparatus and methods protect state in a file system using a message-passing multi-threaded journal. One example apparatus stores, in memory, data and metadata affected by a file system transaction. The apparatus may run a thread that receives the file system transaction from the file system and that produces a set of atomic operations configured to complete the file system transaction. The apparatus may also run a thread that records a set of journal entries associated with the set of atomic operations to protect the file system while the atomic operations complete. The journal entries may be written on a non-volatile computer-readable medium. The apparatus may also run a thread that co-ordinates usage of space on the computer-readable medium. Rather than synchronizing journal activity with locks, the threads running on the example apparatus may synchronize their activity using message passing.

Abstract: One example method presents a synthetic view of data stored by a shared device file system. The synthetic view provides a “fictional” single namespace for data stored by the shared device file system. The method includes accepting a command to access data stored by the shared device file system. The command may be native to a user requesting the access. The command addresses the data stored by the shared device file system using the single namespace provided by the synthetic view. The method includes creating a replacement command(s) for accessing data stored by the shared device file system using one or more actual namespaces different from the single fictional namespace provided by the synthetic view. With the replacement command(s) prepared, the method proceeds to access data stored by the shared device file system using the replacement command(s).

Abstract: Apparatus, methods, and other embodiments associated with providing front end intelligence for monitoring back end state are described. One example method includes controlling a first entity to request that a second entity perform a multi-state stateful operation (e.g., file create). The method includes receiving notice from the second entity that the stateful operation has attained a first state (e.g., partial file create complete) and, upon receiving the notice, maintaining, at the first entity, information (e.g., sequence number, metadata) associated with the stateful operation. The method also includes, upon receiving notice that the second entity lost state before the stateful operation attained a second state, selectively providing to the second entity a portion of the information maintained at the first entity, and upon receiving notice from the second entity that the stateful operation has attained the second state, terminating maintaining the information associated with the stateful operation.

Abstract: Example apparatus and methods protect state in a file system using a message-passing multi-threaded journal. One example apparatus stores, in memory, data and metadata affected by a file system transaction. The apparatus may run a thread that receives the file system transaction from the file system and that produces a set of atomic operations configured to complete the file system transaction. The apparatus may also run a thread that records a set of journal entries associated with the set of atomic operations to protect the file system while the atomic operations complete. The journal entries may be written on a non-volatile computer-readable medium. The apparatus may also run a thread that co-ordinates usage of space on the computer-readable medium. Rather than synchronizing journal activity with locks, the threads running on the example apparatus may synchronize their activity using message passing.

Abstract: Example apparatus and methods reserve space in a journal using an observation based approach instead of a fixed sized approach or a worst case scenario approach. One example method receives a request to allocate space in a journal to support a file system transaction. The example method reserves an amount of space in the journal based on a pre-existing reservation size estimate. Unlike conventional systems, the estimate is not based on a worst-case scenario. The example method observes the actual amount of storage used in the journal by the file system transaction and then selectively automatically adjusts the pre-existing reservation size estimate. The estimate may slowly shrink if no overflows are encountered but may quickly grow if an overflow is detected.

Abstract: Example apparatus and methods concern controlling a computer to prevent read while writing occurrences in direct output. One example method includes identifying a non-conformance between a block of data intended to be output using direct output and a desired direct output block. Conventionally, the non-conformance would cause the computer to perform a read operation to provide additional data suitable for conforming the block of data to the desired direct output block. Once the method has identified the non-conformance, the method may prevent the computer from performing the read operation. The method may also control the computer to perform an additional output operation to make the block of data appear to conform to the desired direct output block. The additional output operation will be performed without performing a read operation. In one embodiment, the method is performed in the kernel of an operating system running on the computer.

Abstract: Apparatus, methods, and other embodiments associated with reducing metadata controller communication volume are described. One example apparatus produces tracking data by tracking metadata controller communications and then controls which of two different types of metadata controller communication message types are used for metadata controller communications based, at least in part, on the tracking data. One message type provides actual state and/or location information about a metadata controller. A second message type provides only information about the state and/or location information available at a metadata controller. Selectively using the second message type facilitates reducing metadata controller communication volume.

Abstract: Apparatus, methods, and other embodiments associated with providing front end intelligence for monitoring back end state are described. One example method includes controlling a first entity to request that a second entity perform a multi-state stateful operation (e.g., file create). The method includes receiving notice from the second entity that the stateful operation has attained a first state (e.g., partial file create complete) and, upon receiving the notice, maintaining, at the first entity, information (e.g., sequence number, metadata) associated with the stateful operation. The method also includes, upon receiving notice that the second entity lost state before the stateful operation attained a second state, selectively providing to the second entity a portion of the information maintained at the first entity, and upon receiving notice from the second entity that the stateful operation has attained the second state, terminating maintaining the information associated with the stateful operation.

Abstract: Example apparatus and methods concern controlling a computer to prevent read while writing occurrences in direct output. One example method includes identifying a non-conformance between a block of data intended to be output using direct output and a desired direct output block. Conventionally, the non-conformance would cause the computer to perform a read operation to provide additional data suitable for conforming the block of data to the desired direct output block. Once the method has identified the non-conformance, the method may prevent the computer from performing the read operation. The method may also control the computer to perform an additional output operation to make the block of data appear to conform to the desired direct output block. The additional output operation will be performed without performing a read operation. In one embodiment, the method is performed in the kernel of an operating system running on the computer.

Abstract: One example method presents a synthetic view of data stored by a shared device file system. The synthetic view provides a “fictional” single namespace for data stored by the shared device file system. The method includes accepting a command to access data stored by the shared device file system. The command may be native to a user requesting the access. The command addresses the data stored by the shared device file system using the single namespace provided by the synthetic view. The method includes creating a replacement command(s) for accessing data stored by the shared device file system using one or more actual namespaces different from the single fictional namespace provided by the synthetic view. With the replacement command(s) prepared, the method proceeds to access data stored by the shared device file system using the replacement command(s).

Abstract: Example apparatus, methods, and computers facilitate improving spatial locality of file system block allocations for related items. One example method includes accessing a block allocation request that is configured to control a computer to allocate a block of storage available on a storage device and, upon determining that the block allocation request includes a session key that identifies a session associated with a block reservation pool, controlling the computer to allocate a block of storage from the block reservation pool to satisfy the block allocation request rather than allocating a block of storage from generally available blocks of storage. The block reservation pool includes blocks of storage on the storage device that satisfy a spatial locality relationship determined by a pre-read technique associated with the storage device.

Abstract: Example apparatus, methods, and computers facilitate improving spatial locality of file system block allocations for related items. One example method includes accessing a block allocation request that is configured to control a computer to allocate a block of storage available on a storage device and, upon determining that the block allocation request includes a session key that identifies a session associated with a block reservation pool, controlling the computer to allocate a block of storage from the block reservation pool to satisfy the block allocation request rather than allocating a block of storage from generally available blocks of storage. The block reservation pool includes blocks of storage on the storage device that satisfy a spatial locality relationship determined by a pre-read technique associated with the storage device.