Hard disk / eMMC on LaserJet Enterprise M553x - reported sizes inconsistent

[dansdaduk]

I'm trying to reconcile various reports, available for the internal hard disk on my (loan) LaserJet Enterprise M553x, with each other and with the published specification (which indicates a 4 GB disk):

The Configuration Page on the Embedded Web Server backs this up (3688 MB, which is close enough to 4 GB given the usual 'rounding' mechanisms used), although it also indicates that the "disk cannot be encrypted":

But the File Directory Page report (one of the reports available from the printer) shows two "devices" (each with "Device Capacity = Free Space", and with a combined total capacity of 1063 MB😞

A PJL INFO FILESYS query generates the following response:

where the indicated capacity is (approximately) 614 MB;

This latter figure is the same as the capacity of the "User data" storage area in the File Directory Page report.

This seems to imply that the PJL FileSystem area is within that storage area.

This appears to be confirmed if a PJL FSMKDIR NAME = "0:\pcl" command is issued to create a new folder at the root of volume 0:

The new folder appears as Directory \PDL\pcl (in a new  File Directory Page report), implying that the PJL FileSystem volume 0: is relative to the directory \PDL in the "User data" storage area.

[As an aside, note that the new folder disappears after the printer is power-cycled; I think that this is because (I suspect) the "hard drive" is actually an embedded MultiMedia Card (eMMC) device, so (at least) the PJL FileSystem part is in volatile, rather than non-volatile storage.]

Can anyone explain the above, in particular:

• Why the File Directory Page report indicates that the disk capacity is only 1063 MB, much less than the 3688 MB capacity indicated elsewhere?
• Why the File Directory Page report indicates that the "Device Capacity = Free Space" for each of the two storage areas described? Is it just that all of the folders mentioned are currently empty?
• Is there any available documentation which explains the purpose of each of the storage areas and directories shown  in the File Directory Page report?
• PJL FileSystem commands only seem to be able to address the \PDL folder within the "User data" storage area; is there anything else which can provide details of what is in the other folders (SNMP? PML?); or (perhaps likely) would such infomation compromise security?

[ShawnR · Accepted solution]

I can try to shed some light on your "File Directory Page" observation.  

What you are seeing is how the eMMC disk space is partitioned and how much free disk space different partitions have and how they are used.  The device has a customer partition and an extensibility partition as you are seeing.  There are also other partitions where we store firmware and device data.  Device data includes settings for the device, usage statistics, color tables, firmware debug logs, OCR engine data, fonts, etc.  So a lot of the 4GB eMMC space is already set aside for firmware, job processing, and machine operating data.  The remaining space is partitioned for the Extensibility or User Data.  

Hopefully this helps.

[dansdaduk]

@ShawnR

Thanks for your response.

The idea that (most of) the "disk" space is taken up with non-volatile items such as firmware (i.e. the various language intepreters, etc.), internal fonts and other reserved areas (logs, etc.)  has vaguely crossed my mind.

So you've answered the main question - thank you.

If you do come across any (non-restricted) documentation which describes the directory structure in more detail, please let me know.