Re: Large Files

From: Rene Brun (Rene.Brun@cern.ch)
Date: Thu Jul 29 1999 - 17:14:42 MEST


Hi Norbert,
I am amused to see that your mail is dated 27 February 1940 !!

Root files are currently limited to 2 GBytes. One of the TFile data
members fUnits describe the number of bytes for the pointers in the
file.
Currently fUnits=4. Setting fUnits to 8 to get 64 bits pointers
requires a few more changes (typedef for Seek_t in particular).

I had the impression that the possibility to get files bigger than 2
GBytes was an urgent topic 2 years ago. Meanwhile, most people have
discovered
that there are probably more drawbacks than advantages in doing that
and I see most collaborations standardizing on a maximum file size
around
1 GByte.

We are willing to test Root with large files if we have access to a
machine/os
supporting large files with at least 8 GBytes of free space that we can
use.

Rene Brun

Norbert Danneberg wrote:
> 
> Hi
> 
> I trying to write a huge Tree to a file. After the filesize reachese
> approx. 2GB the algorith crashes and leaves the file impropper closed.
> 
> -rw-r--r--   1 muptdev  users    1999999972 Jul 28 20:12
> /data_sdc/mt615xNeg_A.cal.root
> -rw-r--r--   1 muptdev  users    1999999995 Jul 29 11:23
> /data_sdc/mt615xPos_A.cal.root
> 
> Is there a limit in file-size ?
> 
> Every time I open the file root recovers 379 keys wich takes some time.
> Ist there a way to permanetly recover the file in such a way that it is
> closed properly afterwards?
> 
> Opening the File in "Updated" mode did also not work. I receive the
> following error:
> 
> root [0] f1 = new TFile("/data_sdc/mt615xPos_A.cal.root","Update");
> Warning in <TFile::TFile>: file /data_sdc/mt615xPos_A.cal.root probably
> not clos
> ed, trying to recover
> Address = 2000000001    Nbytes = 0      =====E R R O R=======
> Error in <TKey::Create>: Cannot allocate 20474 bytes for ID =
> /data_sdc/mt615xPos_A.cal.root Title =
> 
> Thanks,
> 
> Norbert
> 
> --
> 
> Norbert Danneberg
> 
> ETH Zurich - Institute for Particle Physics
>   Laboratory for Nuclear Physics          Phone.: +41-1-633-2034
>   Hoenggerberg                            Fax.:   +41-1-633-1067
>   CH-8093 Zurich
> 
> ETH Zurich - Institute for Particle Physics
>   Paul Scherrer Institute                 Phone.: +41-56-310-3284
>   CH-5232 Villigen PSI                    Fax.:   +41-56-310-4362
> 
> email: Norbert.Danneberg@psi.ch



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