Date: Wed, 17 Sep 1997 09:09:54 -0400 (EDT) From: Chuck Robey <chuckr@glue.umd.edu> To: Simon Shapiro <Shimon@i-Connect.Net> Cc: FreeBSD-Hackers <FreeBSD-Hackers@FreeBSD.ORG> Subject: Re: Distributed Lock Manager on FreeBSD (fwd) Message-ID: <Pine.BSF.3.96.970917090654.2465A-100000@Journey2.mat.net>
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---------- Forwarded message ---------- Date: Wed, 17 Sep 1997 04:21:46 +0000 (GMT) From: Alfred Perlstein <perlsta@fang.cs.sunyit.edu> To: Simon Shapiro <Shimon@i-Connect.Net> Cc: FreeBSD-Hackers@FreeBSD.ORG Subject: Re: Distributed Lock Manager on FreeBSD > We are putting the finishing touches on a true general purpose distributed > lock manager for FreeBSD. This message is a solicitation for interest. If > I receive enough interest in it I will start a chain of discussions on the > subject and solicit core review for inclusion in FreeBSD. This may not be > easy as some of my management would like to keep it proprietary. > > To illustrate, an Oracle equivalent (subset, really) had a cost of over > $250,000 for the source and about 1/5 for binary. > I'm impressed! This is a huge undertaking. I'd love to read more, I hope you post updates, or give URL's where I can read more about it. > > VERY BRIEF SUMMARY: > > DLM is a method by which cooperating processes on different machines (even > different operating systems) can inform each other of interest in a named > object. Just like a database lock manager, or a file system lock manager, > but with the ability to span hosts in real time. > > Some highlight of this DLM: > > * Kernel implementation; All the locking logic is in the O/S kernel, not > in userspace. > > * Multi-state, hirerchial lock with up to 32 states per lock. > > * Conflict resolution built in; Caller can specify which states to > consider in conflict analysis. > > * Conflict Blocking; Caller can specify which conflict to block on. > > * Programmable conflict block; Allows caller to specify how long to wait. > > * Multiple-locking. Individual states can accumulate; A locker can > specify that multiple ``read'' locks are permitted. the DLM will > track how many are actually applied. > > * Remote Locking; A call to the local DLM agent for locking a remote > resource is automatically proxied. > > * Shared Locking; If a resource is shared, the DLM will apply both local > and remote lock and automatically/instantly resolve deadlocks. > > * Multi-path; Each resource can have its own data path (TCP/IP, SCSI, > RCS-232, etc.) UDP support is running, SCSI support via DPT is > forthcoming. > > * External resource management; The mapping of resources is external to > the locking agent. > > * Distributed; There is no central locking authority, although you can > easily create one via resource configuration. > > + What is it good for? We are using it to build our non-stop RDBMS server, > which is composed of a group of FreeBSD machines tied to a single disk > farm. The RDBMS is PgSQL with the lock manager replaced with the DLM and > the storage manager replaced with the DBFS/DIO module I am still working > on. > > If any of this is of any interest to any of you, drop me a line. Please > try to do so soon , so I can decide how to document the thing. > > > > --- > > > Sincerely Yours, (Sent on 16-Sep-97, 19:18:09 > by XF-Mail) > > Simon Shapiro Atlas Telecom > Senior Architect 14355 SW Allen Blvd., Suite 130 Beaverton OR 97005 > Shimon@i-Connect.Net Voice: 503.643.5559, Emergency: 503.799.2313 > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------
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