Re: [Prevayler-discussion] Dual Logging
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jsampson,
klauswuestefeld
From: <pe...@ob...> - 2002-11-05 13:55:09
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Hi, Such a constructor (int commandLogParallelism) already exists. Stefan, another idea is to set up your OS to use some redundancy mechan= ism in the file system, like disk or volume mirroring. In this way, you wou= ld always have 2 or more identical copies of your prevalencebase, controll= ed automatically by your OS. Do you have this possibility in your OS? Peccin >>BTW, does anyone actually use the possibility of >> >> >naming more than one > > >>logging directory in the SnapshotPrevayler constructor >> >> >(which splits, > > >>not replicates the logs)? To me, this strongly smells >> >> >like a solution to > > >>a non-problem :) >> >> > >Consider a single huge atomic command that takes several >seconds to serialize. You cannot block the whole system >to do that. > I see the merit in the feature itself. My question concerns the interface: passing an array of directories seems a bit awkward to me. = I can't imagine why you would want to pass a number of _different_ directories. To recover the database, you need all the logs anyway, so why spread them among multiple directories? So I think it would make more sense to give to the constructor the number of logs to be written concurrently (5 by default) and just one directory name: SnapshotPrevayler(PrevalentSystem newSystem, String commandLogDirectory= , int commandLogParallelism, String snapshotDirectory) { ... } -Stefan > >But I would also like to know if anyone is using/would >really use that. The problem is that is still in the >alpha version... > >See you, Klaus. > > > > >>---------- In=EDcio da mensagem original ----------- >> De: prevayler-discussion- >> >> >ad...@li... > > >> Para: pre...@li... >> Cc: >> Data: Tue, 05 Nov 2002 01:23:35 +0100 >>Assunto: [Prevayler-discussion] Dual Logging >>Hey, the list's been really quiet these days... >> >>What I'm thinking about today is a mechanism to write l >> >> >ogs to more than > > >>one directory at a time. >> >>The setting: I have a webserver with two hard disks. Th >> >> >e second disk is > > >>used as a backup medium. Currently I'm .tar.gz- >> >> >ing the whole > > >>PrevalenceBase directory every hour and store the archi >> >> >ve on the second > > >>disk. A suboptimal solution to say the least. >> >>What I would like Prevayler to do is automatically writ >> >> >e command logs to > > >>both disks. This way, there's always an up-to- >> >> >date backup. Snapshots > > >>should also be written to both disks. It would be perfe >> >> >ct if it worked > > >>like this: After writing a snapshot (if there wasn't an >> >> > exception!), all > > >>previous snapshots and old command logs on disk 1 are d >> >> >eleted. On disk > > >>2, they remain. Thus, disk 1 always contains the minima >> >> >l set of files > > >>necessary to restore the database. Disk 2, on the other >> >> > hand, holds a > > >>complete history of the database, allowing to recover p >> >> >revious states. > > >>So on the API side, we need: >>-Specification of multiple snapshot+logging directories >>-A "keep history" flag for each directory >> >>Any thoughts on how to add this most elegantly? >> >>BTW, does anyone actually use the possibility of naming >> >> > more than one > > >>logging directory in the SnapshotPrevayler constructor >> >> >(which splits, > > >>not replicates the logs)? To me, this strongly smells l >> >> >ike a solution to > > >>a non-problem :) >> >>-Stefan >> >> >> >>------------------------------------------------------- >>This SF.net email is sponsored by: ApacheCon, November >> >> >18-21 in > > >>Las Vegas (supported by COMDEX), the only Apache event >> >> >to be > > >>fully supported by the ASF. http://www.apachecon.com >>_______________________________________________ >>To unsubscribe go to the end of this page: http://lists >> >> >.sourceforge.net/lists/listinfo/prevayler-discussion > > >>_______________________________________________ >>"Do you still use a database?" -- >> >> > http://www.prevayler.org > > > > >______________________________________________________________________= ____ >Encontre sempre uma linha desocupada com o Discador BOL! >http://sac.bol.com.br/discador.html >Ainda n=E3o tem AcessoBOL? Assine j=E1! http://sac.bol.com.br > > > > >------------------------------------------------------- >This SF.net email is sponsored by: ApacheCon, November 18-21 in >Las Vegas (supported by COMDEX), the only Apache event to be >fully supported by the ASF. http://www.apachecon.com >_______________________________________________ >To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion >_______________________________________________ >"Do you still use a database?" -- http://www.prevayler.org > > > ------------------------------------------------------- This sf.net email is sponsored by: See the NEW Palm Tungsten T handheld. Power & Color in a compact size! http://ads.sourceforge.net/cgi-bin/redirect.pl?palm0001en _______________________________________________ To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion _______________________________________________ "Do you still use a database?" -- http://www.prevayler.org = |