UNIX System Administration Handbook - Evi Nemeth [129]
Pros:
• Backed by IBM; it’s here to stay
• Attractive pricing and leasing options
• Very low failure rate
• Uses disk cache; useful for backing up slow clients
• Deals with Windows clients
• Excellent documentation (priced separately)
Cons:
• Poorly designed GUI interface
• Every 2 files =1K in the database.
• The design is incremental forever
Veritas
Veritas sells backup solutions for a variety of systems. When you visit their web site (www.veritas.com), make sure you select the product that’s appropriate for you.
Pros:
• Decent GUI interface
• Connects directly to Network Appliance filers
• Push install for UNIX
• Can write tapes in gnutar format
• Centralized database, but can support a distributed backup system
Cons:
• Some bugs
• Didn’t support DHCP clients (may have changed by now)
• Pricing is confusing and annoying
• NT support was spotty
Legato
Legato backup software is sold directly from Legato, but it’s also bundled by some major computer manufacturers, such as Compaq. More information can be found at www.legato.com.
Pros:
• Nice GUI
• Very reasonably priced
• Automatic mail to users informing them of backup status
Cons:
• Some problems with a corrupted index file
• Not recommended for 100+ clients
• Didn’t support heterogeneity of clients (even though advertised to do so)
• Couldn’t handle a large filesystem
• Poor support
Other alternatives
W. Curtis Preston, author of the O’Reilly backup book, maintains a very useful web page about backup-related topics (disk mirroring products, advanced filesystem products, remote system backup products, off-site data-vaulting products, etc.). Among other resources, it includes an extensive table of just about every piece of commercial backup software known to mankind. We recommend both the book and the web site highly. The address is www.backupcentral.com.
1. That is, unless you have a stacker, jukebox, or library, and your version of dump supports it.
2. A large financial institution located in the World Trade Center kept its “off-site” backups one or two floors below their offices. When the building was bombed, the backup tapes (as well as the computers) were destroyed. Make sure “off-site” really is.
3. restore t reads the directory for the dump, which is stored at the beginning of the tape. When you actually go out and restore a file, you are testing a more extensive region of the medium.
4. Holes are blocks that have never contained data. If you open a file, write one byte, seek 1MB into the file, then write another byte, the resulting file will take up only two disk blocks even though its logical size is much bigger. Files created by dbm or ndbm contain many holes.
5. dump requires access to raw disk partitions. Anyone allowed to do dumps can read all the files on the system with a little work.
6. Actually, most versions of dump do not keep track of files that have been deleted. If you restore from incremental backups, deleted files will be recreated.
7. All the entries for a tape unit use the same major device number. The minor device number tells the driver about special behaviors (rewinding, byte swapping, etc.).
8. You could instead use the ssh command here for added security.
9. The star next to iamlost indicates that it has been marked for extraction.
10. Some versions of dump and restore are rumored to keep track of deletions. We believe Solaris and Linux to be among these.
11. The GNU implementation includes a filename mapping table as one of the files in the archive. Users of the standard tar can extract the contents of the archive and fix it up by hand, but the process is tedious.
12. GNU’s tar will handle holes intelligently if you invoke the -S option when creating an archive.
RECOMMENDED READING
PRESTON, CURTIS W. Unix Backup and Recovery.