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Re: BDB memory cache problem
Szuts Attila wrote:
The BDB cache resides in memory-mapped files by default. So there is no
step 2, all writes to the memory buffer are automatically paged to disk
by the operating system.
Is there any way to turn off BDB memory_cacheing_to_disk ?
(__db.001 and other files) At least for write operations?
Most of the times this files causes data loss, when OS system crashes.
If I unterstand it right:
1. BDB waiting until memory buffer is full,
2. then write data to disk I/O buffer
3. then will be written data to *.bdb files.That's what the db_recover command is for, to replay events from the log
files back into the database.
Between 1 and 2 data is written to log.000000* file, but after OS recovering
there is always some data I can't read.
If OS fails and BDB memory buffer is not flushed, then data will loss. As I see this is
persistent problem in BDB over the time.
-- Howard Chu
Chief Architect, Symas Corp. Director, Highland Sun
Symas: Premier OpenSource Development and Support