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use of DB_CHKSUM for a bit of extra safety

From: C.A.T.Magic <c.a.t.magic_at_gmx.at>
Date: 2004-04-07 01:00:58 CEST


I just read the document
mentioned in another thread here and would like to know
if anybody has tried to enable the berkeley database feature
which enables an extra SHA1 checksum on each database block
and should give some extra safety for the database.

the berkeley manual says:
  If the operating system writes the first 16KB of the database page
successfully, but crashes before being able to write the second 16KB of
the database, the database has been corrupted and this corruption may or
may not be detected during recovery. For this reason, it may be
important to select database page sizes that will be written as single
block transfers by the underlying operating system. If you do not select
a page size that the underlying operating system will write as a single
block, you may want to configure the database to use checksums (see the
DB_CHKSUM flag for more information).
Do checksum verification of pages read into the cache from the backing
filestore. Berkeley DB uses the SHA1 Secure Hash Algorithm if encryption
is configured and a general hash algorithm if it is not.

has anybody experience with this feature?
how much does it affect performance on large repositories?
is it safe (recommended?) to enable for svn repos?
or is it enabled by default?
I couldn't find this flag mentioned in the svn sourcecode.

thanks for any tips/experiences,

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Received on Wed Apr 7 01:01:34 2004

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