CDs and DVDs are routinely used to back up files and folders from systems. But any administrator who does this with directory structures that have long file names or extremely deep paths that exceed 180 characters will often run into problems.
The Joliet file system, the default used on most writeable-disk media, has a limit of 128 characters in length, but there are four ways to consistently get around this.
Pre-archive the files. Use an archiving program such as NTBACKUP, WinRAR or plain old UNIX gzip/tar to store the directory tree in question in a single archive. This way the directory information is stored in a format that has nothing to do with the limitations of the file system you're copying to. Once you've compressed everything, simply burn the archive to disk.
This is the easiest method, since it allows you to use plain old Joliet or ISO 9660 storage as is. The drawback to this method is that access to individual files is s-l-o-o-o-o-w. I've tried directly opening a 2GB .ZIP archive stored on a DVD-R and the time it takes to enumerate the contents of the archive is agonizingly long. But if you don't mind having to copy the archive out to a hard drive before unpacking a file from it, this is an effective solution.
Use the ISO 9660:1999 filesystem. Also known as ISO Level 2 Long, 9660:1999 is a variant of the ISO 9660 file system standard that has better support for long file names. It supports pathnames up to 207 characters long and allows for directories to be nested more than eight deep.
The only downside here is that a disk created in this format might not be readable on all computers. Although it's supported by most applications that burn to CD, for instance, Nero 6 and higher, some applications do not support burning ISO 9660:1999 to DVD.
Use the UDF filesystem. UDF is another commonly supported mass storage file system that doesn't have Joliet's length restrictions. UDF 1.5 and higher can support individual file names of 255 bytes and a maximum pathsize of 1023 bytes.
The downside here is that many systems still don't read UDF natively. But if you're only reading the discs in a system that can (Windows XP can read UDF natively), this shouldn't be a concern.
Avoid long pathnames to begin with. The obvious answer! I know that sometimes it's not possible, but it's worth mentioning if only because it encourages planning ahead. If you know that archiving to CD/DVD is going to be part of the plan, try structuring the directories of what's to be archived to avoid excessively long pathnames. This may not be as hard to cope with as you think, and it will make navigating the file system a lot easier to begin with.
About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter. Check it out for the latest advice and musings on the world of Windows network administrators -- and please share your thoughts as well!
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