Title: +038=360.000-OU045T_02-PCD2.m4160 PLS SBC - File system Manual.pdf
The compression of a flash device is a complex task that copies all used data of a sector to a reserved sector and then erases the sector to be compressed. After the erase process (which takes about 2 seconds) the used data is copied back to its original sector (and the reserved sector is erased as preparation for the next cycle). After the compression, there is no more “freed” memory on the compressed sector and therefore all unused memory can be written.By default the compression of the device is triggered automatically (based on the ra- tio of used, freed and available memory on the device). During the compression of a flash device, this device can not be accessed and is marked as “busy”. This can lead to the fact that e.g. a download of a file using FTP fails because the Saia PCD® starts compressing in the middle of the download.In order to avoid this kind of trouble it is recommended compressing the device by either the user program or the CGI calls on the Saia PCD® Web Server.1)