Samba4: LDB size limit and memory leak

Andrew Bartlett abartlet at
Wed May 27 01:50:39 GMT 2009

On Mon, 2009-05-25 at 09:23 +0200, Marcel Ritter wrote:
> Andrew Bartlett schrieb:
> > On Mon, 2009-05-25 at 08:30 +0200, Marcel Ritter wrote:
> >   
> >> Hi,
> >>     
> Hi Andrew,
> >> I'm running several samba 4 tests at the moment and I found two things,
> >> that may need some attention:
> >>
> >> 1. LDB size seems to be limited to 4GB (both on i586 and x86_64). I tried
> >>     to create a lot of new users using setup/newuser and somewhere in
> >> between
> >>     20000 and 40000 users, setup/newuser crashes:
> >>     
> >
> > Correct.  If a 64 bit varient of TDB were developed, that limit would be
> > removed.
> >   
> So TDB is 32-bit only right now?
> In bugzilla I found something about a 64-bit Patch to TDB, but it's quite
> outdated (from 2005):

Moving TDB to a 64 bit database is more about changing the on-disk
format, and making improvements to the internal structure that would
better suit a database of this size. 

However, In retrospect, I'm surprised that you found the limit to be a
20,000 users.  This seems rather small:  We should expect users to only
take up 2k each, with an additional overhead for indexes.  

> Any hint what needs to be done to make it 64-bit capable?
> >>    The resulting filesize of users.ldb is exactly 4GB + 4096 bytes
> >> (4294971392 bytes)
> >>

I think what's happening here is actually that you didn't add all the
users in a single transaction, and as such are hitting up against the
pathological database growth issues we first saw late last year.

I think we need some internal trigger to say 'repack the database' (ie
call tdb_repack())

As a test, can you keep adding records if you call tdbbackup on the
users.ldb (and then replace users.ldb with the backup)?

Andrew Bartlett

Andrew Bartlett                      
Authentication Developer, Samba Team 
Samba Developer, Red Hat Inc.        

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