The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 02, 2003
Filed:
Jan. 10, 2000
Ira Pramanick, San Jose, CA (US);
Declan J. Murphy, San Francisco, CA (US);
Krishna K. Kumar, Cupertino, CA (US);
Siamak Nazari, Arcadia, CA (US);
Andrew L. Hisgen, Cupertino, CA (US);
Sun Microsystems, Inc., Santa Clara, CA (US);
Abstract
Method for emulating persistent group reservations on non persistent group reservation-compliant devices, apparatus to perform the method, and computer-readable storage medium containing instructions to perform the method. The present invention enables the emulation of persistent group reservations on a non persistent group reservation-compliant device, including a shared disk, to enable the disk's implementation of persistent group reservation-reliant algorithms. This in turn enables the implementation of algorithms based on persistent group reservation features substantially without modification of those algorithms. One such algorithm is a quorum algorithm. One example of persistent group reservations is found in the SCSI-3 standard. The present invention accomplishes persistent group reservation emulation, or PGRE, by storing host- and reservation-specific information on a reserved portion of the disk and using this data to emulate the steps of certain persistent group reservation features. One persistent group reservation preempt feature executes a set of steps as a single atomic action, the mutual exclusion necessary for this feature being done internally by the persistent group reservations-compliant device. To emulate this feature, the present invention uses mutual exclusion algorithm, where the disk serves as the “shared memory” of the algorithm. The variables needed by the algorithm are also stored in the reserved portion of the disk.