Disk graphs intermittantly missing disk info (resent in plaintext)

["Brand, Thomas R." <TRBrand (at) cvs.com>]

[Apparently there was a problem the first time I sent this... 
trying again, text only...]

Problem:  Disk Utilization graphs are not showing the correct
information when one partition is not mounted. Disk utilization trend
graphs are not consistant in displaying the information.

I am monitoring 3 file systems: '/', '/data, and '/backup'.

The /backup partition is only mounted while backups are actually 
running which only takes a few minutes.  When the backup completes, 
the /backup drive is unmounted. 

In all cases, the text (from 'df') on the web page correctly lists the 
partitions that are mounted and correctly displays any disk space
alerts:
--------------------
/data (27% used) has reached the WARNING level (25%)

Filesystem         1024-blocks      Used Available Capacity Mounted on
LABEL=ROOT1            8652060   3039788   5172772      38% /
/dev/sda7             14740312   3753364  10238176      27% /data
--------------------

When the backup partition is mounted, the disk utilization image 
displays all three partitions in the line graphs and lists all 3 
backup' with the cur/max/min/avg data below the line graph.

When the backup partition is not mounted, the image displays only 
the '/' root and '/backup' partition in the line graph, and only lists 
'/' and '/backup' with the cur/max/min/avg data below the line graph.
The '/data' partition is not displayed/listed anywhere in the image.


Looking for some suggestions as to why / how this is happening and 
if there is something I can do to fix this.

thanks for any suggestions/pointers,
Tom