For all its sexiness, CAS is a complicated solution to the problem of preventing users and admins from deleting or modifying files. Several vendors, including Network Appliance through its optional SnapLock for filers running OnTap and Sun's StorageTek division through its StorEdge Compliance Archiving software, have added software-managed WORM to their NAS appliances. Organizations can use the same NAS architectures, even the same appliances, as their primary file stores and still have a WORM archive. One system for backup, replication, and management saves money and complexity.
Locked NAS is also easy on your developers. Rather than having to integrate a new XML-based API, they can simply write to the locked NAS via CIFS or NFS. Data-retention periods can be defined on a folder-by-folder, or even a file-by-file, basis by setting the "file last accessed" time attribute to the end of the retention period and then flagging the file as read only.
Now that Network Appliance has rolled out its proprietary Advanced Single Instance Storage (A-SIS) subfile data deduplication technology, a NetApp filer running SnapLock can one-up the CAS vendor's single-instance storage, eliminating not just duplicate files but also duplicate data within files, ensuring that those five corporate positioning slides that appear in almost every PowerPoint presentation will be stored only once.
Compared with CAS, locked NAS does lack a mechanism for storing metadata about objects. How big a problem that is depends on how good your archiving software is. CAS systems provide an XML interface for storing file metadata, but organizations selecting locked NAS as their compliance stores will need to look to their archiving software or enterprise content management systems as a metadata store.
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