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From Øystein Grøvlen <Oystein.Grov...@Sun.COM>
Subject Re: Discussion of incremental checkpointing
Date Fri, 17 Feb 2006 21:27:13 GMT
Look likes a good plan (if you have time enough to do all you suggest). 
     In case your aiming for a certain recovery time, it would be good 
to run experiments to evaluate how accurate your estimates are.  I.e., 
how long does the recovery actually take.


Raymond Raymond wrote:
> Thanks for so many people gave their suggestions on this issue.
> I really learned a lot of things from it. Since I am doing a student 
> project
> on derby, I am thinking of implementing two versions of checkpointing:
> 1. Let me call it "automaticaly scheduled checkpointing". In this version,
> I will not change lots on the checkpointing mechanism. I will add a module
> to schedule the checkpointing automaticaly depends on the system
> performance what we have discussed before( e.p. recovery speed,
> current disk I/O situation).The only thing I will change on the
> checkpointing process is to make it wirte out several pages and sleep
> for a while if the system is busy, and then write several more,and so on.
> 2. Let me call it "Incremental checkpointing"(details please refer to the
> former discussions).
> Then I want do some test and comparison among:
>  -- The current checkpointing mechanism
>  -- The automatically scheduled checkpointing mechanism
>  -- The incremental checkpointing mechanism
> and we can know which one would be better.
> I still have a questions about derby checkpointing. Someone can
> help me to make it clear? ^_^.
> I want to summarize what events will trigger a checkpoint?
> On the derby website :
>   http://db.apache.org/derby/papers/logformats.html
> I found such comments:
> -------------------------------------------------------------------------------------------------------------------------------------------

> With the default values, a new log file is created (this is known as log 
> switch) when a log file grows beyond 1MB and a checkpoint happens when 
> the amount of log written is 10MB or more from the last checkpoint.
> RawStore exposes a checkpoint method which clients can call, or a 
> checkpoint is taken automatically by the RawStore when:
> 1. The log file grows beyond a certain size (configurable, default 1MB)
> 2. RawStore is shutdown and a checkpoint hasn't been done "for a while"
> 3. RawStore is recovered and a checkpoint hasn't been done "for a while"
> -------------------------------------------------------------------------------------------------------------------------------------------

> I am no very clear about what " for a while " means in the second and 
> the third comments.
> I also want to know is there any other events will trigger a checkpoint 
> besides these?
> Thanks.
> Raymond
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