VERITAS Storage Foundation 4.1 Cross-Platform Data Sharing Administrator's Guide

Considerations About Data in the File System
38 VERITAS Storage Foundation CDS Administrator’s Guide
Considerations About Data in the File System
Data within a file system might not be in the appropriate format to be accessed if moved between
different types of systems. For example, files stored in proprietary binary formats often cannot be
transferred as is. Files containing databases might not be in a standard format that allows their
access when moving a file system between various systems, even if those systems use the same
byte order.
Some data is inherently portable, such as plain ASCII files. Other data is designed to be portable
and the applications that access such data are able to access it irrespective of the system on which it
was created, such as Adobe PDF files.
Note that the CDS facilities do not convert the end user data. The data is uninterpreted by the file
system. Only individual applications have knowledge of the data formats, and thus those
applications and end users must deal with this issue. This issue is not CDS-specific, but is true
whenever data is moved between different types of systems.
Even though a user might have a file system with data that cannot be readily interpreted or
manipulated on a different type of system, there still are reasons for moving such data by using
CDS mechanisms. For example, if the desire is to bring a file system off line from its primary use
location for purposes of backing it up without placing that load on the server or because the system
on which it will be backed up is the one that has the tape devices directly attached to it, then using
CDS to move the file system is appropriate.
Another example is a principal file server that has various file systems being served by it over the
network. If a second file server system with a different operating system was purchased to reduce
the load on the original server, CDS can migrate the file system instead of having to move the data
to different physical storage over the network, even if the data could not be interpreted or used by
either the original or new file server. This is a scenario that often occurs when the data is only
accessible or understood by software running on PCs and the file server is UNIX or Linux-based.
File System Migration
File system migration refers to the system management operations related to stopping access to a
file system, and then restarting these operations to access the file system from a different computer
system. File system migration might be required to be done once, such as when permanently
migrating a file system to another system without any future desire to move the file system back to
its original system or to other systems. This type of file system migration is referred to as one-time
file system migration. When ongoing file system migration between multiple systems is desired,
this is known as ongoing file system migration. Different actions are required depending on the
kind of migration, as described in the following sections.