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Re: I lost 7 bdb repositories yesterday!

From: Saulius Grazulis <grazulis_at_akl.lt>
Date: 2005-07-05 09:04:28 CEST

On Tuesday 05 July 2005 04:31, Adrian Hoe wrote:

> > Because BDB is a library that provides ACID features, easily linked  
> > into any program.  Asking people to set up a full SQL system is a  
> > huge barrier to entry.
>
> But reliability is more then easy integration/setup. We have systems  
> running on MySQL with more than 250 tables and over 7 millions tuples  
> and not crashing at all.

But BDB was chosen _because_ it is reliable, wasn't it? And many people are
using it without problems.

My impression is that for BDB, the requirements on the file system are
stricter than those for FSFS. This is because BDB is a _generic_ database,
designed to add/delete/update many records/min efficiently and reliably. It
_is_ reliable, provided certain pre-conditions are met. Unfortunately, quite
often the pre-conditions are broken, and BDB fails in mysterious ways.

I infer this from the fact that BDB doesn't not work on network (nfs) mounted
shares. My guess would be that locking is not atomic enough on these
filesystems for a true database... Or something like this.

The FSFS is designed for just one particular use -- subversion. E.g. it does
not need to delete or update revisions, just to add them ;). Thus, the
pre-conditions for it to work correctly are weaker. So they are more often
satisfied. And it gives overall impression of more reliable system.

-- 
Saulius Gražulis
Visuomeninė organizacija "Atviras Kodas Lietuvai"
P.Vileišio g. 18
LT-10306 Vilnius
Lietuva (Lithuania)
tel/fax:      (+370-5)-210 40 05
mobilus:      (+370-684)-49802, (+370-614)-36366

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Received on Tue Jul 5 08:58:05 2005

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