Understanding the MirrorMaster File transfer:
When a MirrorMaster needs to send or receive a file, it first takes a snapshot of the existing file and names the snapshot the same as the existing file and in the same directory, except that it will have a ~ extension, for ex. "file.txt" becomes "file.~txt". This file is then used until the compete transfer is done and then renamed to the existing file.
Understanding MirrorMaster File comparisons:
A MirrorMaster client first gets a list of flow files from the master MirrorMaster which it then uses to compare against it's flow's local filelist. Each file is compared in:
| • | File Name, i.e. does the file exist or not? |
| • | File Size, i.e. does the remote and local file sizes differ? |
| • | File Stamp, i.e. does the remote and local file modified date-times differ? |
| • | File CRC, i.e. does the actual file contents differ? |
If any one of these criteria is true, then the file will be transferred. After a file is completely transferred and renamed to the correct file, the newly transferred file is re-timestamped to the exact same modified date-time of the remote MirrorMaster such that the two files will no longer differ with the next replication (unless, of course, someone again updated the file)
Understanding MirrorMaster RAM requirements:
In order for your MirrorMaster to send or receive a file, the file will be loaded into memory during the transfer process. Therefore, if 10 MirrorMaster clients connect to you at the same time and each is transferring a 50MB file, then you will temporarily need 500MB of RAM. For this reason each MirrorMaster has defined a Buffer property which can be set as low as 1 byte (default is 32768 bytes). If a file is larger than this limit, it will be transferred in chunks no larger than this value and therefore you will need only 32768x10=300KB of RAM for our previous example.