Re: Results of CheckDS.py

On Wednesday 07 February 2007 12:17, Ed Leafe wrote:

> 29729292561 bytes in object files
>       43945 transactions
>      245355 revisions of objects
>      120467 objects
>     6737567 bytes in transaction files
> 29736030128 total bytes

These statistics are all perfectly normal

>       37709 data files whose transaction file is not linked into history
>           4 data files with no corresponding transaction file

These are nothing to worry about. At some point the packing process has been 
interrupted mid-way through.

>          19 object data files with bad md5 checksum

This is worrying. 19 files have changed on disk since they were written by 
DirectoryStorage. ZODB will not be able to load these 19 objects (assuming 
these data files are the current revision of each oid). You will not be able 
to pack.

This could be a DirectoryStorage bug, but is more likely to be bad RAM, bad 
disk or disk controller, etc. The other output of checkds will log the names 
of these 19 files; it may be interesting to inspect them.
(and I would be interested to receive copies by private email)

If you have good copies of these files in an old backup it will be safe to 
copy them into your current working directory, replacing the corrupt ones.

>       26316 maximum referencee graph depth
>      2883.1 average reference graph depth

This is interesting, but not a problem. It indicates that a heuristic which 
minimises memory usage during packing is sub-optimal for your dataset.

[The "maximum reference graph depth" determines the memory usage of the 
packing process. This is determined by the traversal order through the ZODB 
object reference graph. Ideally it should be approximately log(number of 
objects). In the worst case it would equal the number of objects. Here it is 
20% of this worst case, which is larger than I have seen previously. As I 
said this is not necessarily a problem. If you later want to experiment to 
reduce memory usage during packing then I may be able to suggest some tweaks]


-- 
Toby Dickenson

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