Revision as of 07:19, 20 August 2007 edit Rank1cheng (talk \| contribs) 7 edits No edit summary ← Previous edit		Revision as of 16:03, 30 August 2007 edit undo Chris Chittleborough (talk \| contribs) Extended confirmed users, Pending changes reviewers, Rollbackers 9,020 edits Restructure (now fairly chronological), add some detail on the Linux clustering file systems. Next edit →
Line 1: A '''distributed lock manager''' (DLM) provides distributed applications with a means to synchronize their accesses to shared resources. ~~Combining~~DLMs ~~two~~have orbeen ~~more~~used ~~computers~~as ~~into~~the foundation for several successful clustered file systems, in which the machines in a [[computer cluster\|cluster]] ~~in which the machines~~ can use each other's hard disks and other drives via a unified [[file system]], ~~offers~~with significant advantages for performance and [[high-availability\|availability]]. ~~DLMs~~The ~~have~~DLM ~~been~~is used ~~as the foundation for clustered file systems with considerable success by using cluster wide locks~~ not only for [[file locking]] but also for coordination of all disk access. [[VMScluster]], the first clustering system to come into widespread use, relied on the [[OpenVMS]] DLM in just this way.▼ ~~==Clusters==~~ ▲Combining two or more computers into a [[computer cluster\|cluster]] in which the machines can use each other's hard disks via a unified file system offers significant advantages for performance and [[high-availability\|availability]]. DLMs have been used as the foundation for clustered file systems with considerable success by using cluster wide locks not only for [[file locking]] but also for coordination of all disk access. [[VMScluster]], the first clustering system to come into widespread use, relied on the [[OpenVMS]] DLM in just this way. [[Red Hat]] and [[Oracle Corporation\|Oracle]] have both developed clustering software for [[Linux]]. Both projects include a DLM modelled on the venerable [[OpenVMS\|VMS]] DLM. (''OCFS2'', the Oracle Cluster File System[http://oss.oracle.com/projects/ocfs2/] has been included[http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=29552b1462799afbe02af035b243e97579d63350] in version 2.6.16 of the official [[Linux kernel]]. Red Hat's cluster software[http://sources.redhat.com/cluster/], including their DLM[http://sources.redhat.com/cluster/dlm/] has been included[http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1c1afa3c053d4ccdf44e5a4e159005cdfd48bfc6] in version 2.6.19) [[Google]] developed ''Chubby'' lock service for distributed systems. Chubby is used by other Google infrastructures like [[Google File System]], [[BigTable]], and [[MapReduce]] to synchronize accesses to shared resources.[http://labs.google.com/papers/chubby.html]▼ ==VMS Implementation== Line 84 ⟶ 78: The OpenVMS DLM periodically checks for deadlock situations. In the example above, the second lock enqueue request of one of the processes would return with a deadlock status. It would then be up to this process to take action to resolve the deadlock — in this case by releasing the first lock it obtained. ==Linux ~~Kernel~~clustering==▼ Both [[Red Hat]] and [[Oracle Corporation\|Oracle]] have developed clustering software for [[Linux]]. [[OCFS\|OCFS2]], the Oracle Cluster File System[http://oss.oracle.com/projects/ocfs2/] was added[http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=29552b1462799afbe02af035b243e97579d63350] the official [[Linux kernel]] with version 2.6.16, in January 2006. Red Hat's cluster software[http://sources.redhat.com/cluster/], including their DLM[http://sources.redhat.com/cluster/dlm/] was officially added to the Linux kernel[http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1c1afa3c053d4ccdf44e5a4e159005cdfd48bfc6] with version 2.6.19, in November 2006. Both systems use a DLM modeled on the venerable [[OpenVMS\|VMS]] DLM.[http://lwn.net/Articles/137278/] Oracle's DLM has a simpler API. (the core function, <code>dlmlock()</code>, has eight parameters, whereas the VMS <small><code>SYS$ENQ</code></small> service and Red Hat's <tt>dlm_lock</tt> both have 11.) ==Google's Chubby lock service== ▲[[Google]] has developed ''Chubby'', lock service for loosely-coupled distributed systems. ~~Chubby~~It is used to synchronize accesses to shared resources by ~~other~~key parts of Google's ~~infrastructures~~infrastructure, ~~like~~including [[Google File System]], [[BigTable]], and [[MapReduce]] ~~to synchronize accesses to shared resources~~.[http://labs.google.com/papers/chubby.html] ==SSI Systems== A DLM is also a key component of more ambitious [[Single-system image\|single system image]] projects such as [[OpenSSI]]. ▲==Linux Kernel== ~~A distributed lock management is added in January 2006 by Redhat people.~~ ==References==

Distributed lock manager: Difference between revisions