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Re: BDB memory cache problem

Do you run db_recover after system crash before starting OL?

Szuts Attila wrote:

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.
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.

I know my problem is not strict OL specific, but I tried all DB_CONFIG option from sleepycat that turns off memory cacheing, logging and so on. I always became:
DB_ENV->set_flags: direct I/O is not supported by this platform


# Cachesize (20Mb)
set_cachesize 0 20971520 1

set_lg_regionmax 262144
set_lg_bsize 2097152
#set_lg_dir /var/log/bdb

# Automatically remove log files that are no longer needed.
# Just use these settings when doing slapadd...
#set_flags DB_TXN_NOSYNC

(OL: 2.2.19, BDB: 4.2.52. + 2 patches, OS: Mandrake 10.0)

(SVN guys has similar problems with BDB. They started to use FSFS under SVN.)


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