Synametrics Technologies

I want to copy very large files from one disk to another with minimal downtime to the application that uses those files. One idea is to use robocopy to copy the files while the files are still in use, shutdown the app, and then run robocopy again to copy the changed files. But robocopy doesn't do block-level-diff copies so a small change to a large file will stil require the whole file to be copied again.

Can syncrify replace robocopy in this process but be able to perform the copy faster by only copying the changed blocks? I know witih rsync, local copies don't normally support block-level-diffs but there is an option to force it.

If you are copying the actual file from one disk to another on the same machine, the rsync protocol is NOT a good choice. That is because, at the very minimum, rsync will at least do one read and one write operation on the disk, which is precisely what happens when you copy files using the operating system's native file copying method. In addition to one read/write operation rsync will also try to match MD5 signatures, which is an extra cost in terms of I/O. Therefore, using rsync with or without Syncrify is not a good choice. We have mentioned that on http://web.synametrics.com/SyncrifyLocalDrive.htm . Bottom line: block level file copying is more expensive than copying the entire file on the same machine.

What you need is VSS, which will allow you to copy the file as another process is modifying it. Although Syncrify can do VSS, I am sure you can do that with just Power Script, which will be more efficient.

Syncrify works best when you're transferring data across multiple computers and particularly when the other machine is on a slow network, such as the Internet.