Notes for FTP Servers Lacking Timestamp Support

SureSync 6 introduces a new FTP engine which supports maintaining the modified date and timestamp of the source file on the destination. Your FTP server must support this functionality and many modern FTP servers do. You can easily determine support by running a test job to the FTP server. If the modified date and timestamp on the destination FTP files are always the time the transfer completed to the FTP, you do not have this support. If the modified date and timestamp match the source copy, you have the support.

The capability to maintain modified date and timestamp is a significant FTP enhancement for SureSync 6. When working with an FTP server that supports this functionality, synchronizing to a FTP path will function just like synchronizing to a UNC path. SureSync will only transfer files which have a newer modified timestamp on the source versus always copying all files from the source as in previous versions.

If you are synchronizing to a FTP server which does not support maintaining the modified date and timestamp, it is strongly recommended that you upgrade to a more modern FTP server. If this is not possible, use the tips below to minimize data transmission.

Notes for FTP Servers Lacking Timestamp Support

If you are copying from an FTP site to a local machine (the FTP site is the source), then there should be no problems with date stamps. The local machine will have the ability to date stamp the files to match the dates from the FTP site and will not have problems telling which files have changed.

However, if you are synchronizing to an FTP site (the FTP site is the destination) you will run into problems related to time and date stamps. FTP is unable to use any date for the file except the upload date. An FTP server will always stamp the file with the date that the upload completed. If you are modifying files locally and then pushing them out to one or more FTP sites you will find that all the files are synchronized to the FTP site every time the job is run because the time stamps will never match. However, there are several ways to approach synchronizing to an FTP to deal with the lack of time and date stamp control.

Using a Recent Master Copy Rule

If files are pushed across FTP after they are modified then the FTP site will always have a newer date until the file is modified again. Therefore, if you set up a Recent Master Copy synchronization from the local site to the FTP site, the only files that will be pushed out are the ones whose local date is more recent. And those are exactly the file you want copied. The drawbacks to this method are that if you delete a file locally it will not be deleted on the FTP site, and if you revert to an older copy of a file on the local side it will never get copied up to the FTP site.

Using a Special Upload Folder

You can set up a special upload folder. Any time someone makes a change that should be replicated to the FTP site they put a copy of the appropriate file(s) in the special folder. You then set SureSync to do a regular synchronization from that folder to the FTP site using the Move method. Once the change is transferred to the FTP site SureSync will delete the copy in the special folder. This will assure that no extra copying is done. Once again you have the problem that local deletes will not be reflected on the FTP site. You also have to be sure that users will copy the file(s) to the upload point when they change something.

SureSync includes the ability to set up date filters on your Rules. This allows you to set up a Mirror Rule that only captures files that have changed since the last time an upload was done, or that have changed in the last day (or hour, or week, depending on the frequency you need). This will delete files when appropriate, but is much more likely to do extra copying than a Recent Master Copy.

Using File Attributes

SureSync also has the ability to filter on file attributes. You could set up a mirror that will only copy files where the Archive attribute is on (for the local copy). This should catch only files that have changed. However, you will end up with one of two problems. If you decide to force the Archive attribute off on the source each synchronization (which SureSync can do for you) so that only new changes will copy next time, you are liable to cause problems for your tape backup product, many of which depend on the Archive flag. If you decide to leave the Archive flag alone on the source (and let the tape backup product change it when it needs to) you will probably be copying unchanged files, and if the backup runs before you upload to the FTP site you may miss files.

If in addition to one of these methods you also set up a full Mirror (with no date restrictions) to run occasionally, it will force the two sides to be in sync again. It will also do extra copying (possibly large amounts) over what is often a slow link, but if it is not needed often this is usually an acceptable trade off.