摘要:
A method and system in data processing system are disclosed for the dynamic scheduling of a plurality of requests to access a disk. Each of the requests is associated with a location on the said disk which each of the requests is attempting to access. A scan queue is established for storing the plurality of requests. The plurality of requests are processed in a sequential order. The sequential order is determined utilizing the location on the disk being accessed by each of the requests. Upon one of the stored requests being urgent, the urgent request is processed. The urgent request is associated with a first location on said disk. Processing of the requests then continues in a second sequential order. The second sequential order is determined utilizing the first location. The next request to be processed is one of the requests which is associated with a physically closest location on the disk.
摘要:
The method and system for improved efficiency and parity calculation in RAID data storage system. RAID data storage systems permit recovery of data in the event of a drive failure by storing a parity value for each stripe of data on a separate drive. Each time data is written to a RAID data storage the parity value for the associated data stripe must be updated. Parity may be calculated utilizing two different algorithms. New parity may be calculated utilizing the old data value, the new data value and the old parity value, or calculated utilizing the new data value and all remaining old data within the associated data stripe. The number of input/output operations required to calculate parity utilizing each algorithm is predetermined and the method requiring the least number of input/output operations is selected, unless data sequentiality is detected. If sequential data is present the parity value is calculated utilizing the new data and all old data in the associated data stripe, even if a greater number of input/output operations are initially required, as further sequential input/output operations will be more efficient.
摘要:
A redundant array of inexpensive disks (RAID) includes a plurality of disk drives organized as a plurality of stripes, wherein each stripe includes a plurality of stripe units. A host processor system sends write commands in write-through mode to a RAID controller, some of which are immediately processed by the controller, and others of which are temporarily stored in a stash. Commands stored in the stash for data writes that only partially fill a stripe may be coalesced with another write command that also only partially fills the same stripe. This coalescing occurs for commands for data writes that span one or more stripes, and that may start or stop in the middle of a stripe, as well as in the middle of a stripe unit. In addition, two different commands for writing data to different stripe units, but from the same stripe, can also be coalesced. The coalescing of write commands in the stash reduces the number of disk I/O's and improves data throughput.
摘要:
Because correct configuration data is essential to the operation of any RAID system, and because multiple copies of the configuration data are kept, not only in the RAID controller itself, but also in each disk drive unit in the configuration, it is imperative that the various copies of the configuration data do not become "out of synchronization", which means that one or more copies of the configuration data are different from one or more other copies of the configuration data. To maintain synchronization of all copies of the configuration data, the current invention compares the configuration data stored in the RAID controllers' NVRAM to that of the current system, and records any new, non-responding, repositioned or unidentified storage devices in a change list. The identities and the attachment points of any storage devices in the change list are then displayed to the user, and various options for correcting the lack of synchronization are provided by enabling one or more function keys that may be selected by the user. One such function key, an "accept change" key, causes the configuration data to be modified by changing the current operational state of any non-responding storage device. A "configuration adjustment" key, when selected by the user, causes the configuration data to be modified to reflect any changes in the attachments points of any repositioned storage deices. An "import configuration" key causes the configuration data to be changed to correspond to that of an unidentified storage device. And a "retry" key gives the user an opportunity to rearrange the system and then re-compares the configuration data in the controller to the current system configuration. When the system is operating in un-attended mode, means are disclosed to automatically perform the "accept change", "configuration adjustment" and "import configuration" functions in priority order so long as the "retry" key has not been enabled. The retry key implies attended operation.