1. Chapter 11 Backups Unix System Administration

2. Backup. Why? Because We Like You. w Why backup at all? Restore from data loss Disaster recovery Archival of old data - possibly for legal reasons

3. In the Media... w Backup devices/media Tape Optical (MO) CDROM (CD-R, CD-RW) DVD-R, DVD-R+W, DVD-RAM Removable Disk (Zip, Jaz, floppy?) Paper?

4. Mr. Nixon’s Preferred Media w There are a variety of tape formats to choose from… QIC Cartridge 60+MB per tape 8mm - 2 to 20GB per tape (native) 4mm - 1.3 to 24GB per tape (native) DLT - Digital Linear Tape - 20 to 35GB per tape (native)

5. 8mm - Coming to Video Soon w Cartridge-based tape derived from the Sony Handycam type video tape w Handycam tapes will work, but data 8mm tapes are of higher quality Drive ModelTape LengthCapacity 8200 1122.3Gb 85001125 85051125 8505XL1607 8900 (Mammoth) 17020

6. Sometimes Smaller Is Better w 4mm Based on DAT (Digital Audio Tape) format Tape FormatTape LengthCapacity DDS-1601.3GB DDS-DC902 DDS-21204 DDS-312512

7. I’ll Have a DLT on Toast w DLT - Digital Linear Tape Tape to reel format, that is, the tape is spool to another reel in the drive. It is not cartridge format. 100% duty cycle Tape FormatCapacity DLT 400020GB DLT 700035GB DLT 800040GB

8. Give Your Data a Big Hug w Compression 8mm, 4mm and DLT drive perform hardware compression Marketing usually uses 2:1 ratio Actual is usually 1.8:1 Compression is based on the type of data you are backing up. Text = most compressible and pre-compressed data = least compressible

9. Do and Doh’s w Do Test your backup periodically Store copies of data offsite Label your backups so you know what’s on them w Doh’s Store your tapes near magnetic or electromagnetic sources The Earth’s background radiation can eventually erase magnetic tapes

10. Cage Match: Stackers Vs. Autoloaders Vs. Jukeboxes w Stacker = autoloader Sequential tape access Feeds next tape into drive when on is ejected w Jukebox Random access to tapes in library

11. Backup $oftware w Commercial Veritas Netbackup Legato Networker IBM ADSM w Free or OS Provided tar cpio dd dump/restore

13. OS Backup Tools w tar - Tape Archiver tar cf /dev/rmt/0 filea fileb filec tar xf /dev/rmt/0 tar tf /dev/rmt/0 w cpio - copy in/out similar to tar, AT&T specific w dd - disk duplicate dd if=/dev/rmt/0 of=/dev/rmt/1 dd if=boot.img of=/dev/rdiskette

14. Who’d Want To Restore a Dump? w Dump and Restore ufsdump and ufsrestore in Solaris Primarily Used to backup partitions/slices Maintains “levels” of backups for doing incremental dumps Restore program has option for interactive shell like file browsing Dump/Restore can be used to backup a partition/slice to another partition/slice

15. Dump Examples ufsdump 0ubf 126 /dev/rmt/0n /dev/rdsk/c0t0d0s0 ufsdump 5ubf 126 /dev/rmt/0n /dev/rdsk/c0t1d0s7 ufsrestore ifs /dev/rmt/0 2 Slice-to-Slice Dump newfs -v /dev/rdsk/c0t1d0s6 mount /dev/dsk/c0t1d0s6 /mnt ufsdump 0f - /dev/rdsk/c0t1d0s7 | (cd /mnt; ufsdump 0f -)

16. Managing Your Tape Worm w mt - Magnetic Tape mt -f /dev/rmt/0 rewind mt -f /dev/rmt/0 erase mt -f /dev/rmt/0 offline mt -f /dev/rmt/0 status mt -f /dev/rmt/0 fsf

17. Good Ol’ AT&T Vs. BSD Again w /dev/rmt/0 - AT&T device name Tape head is left positioned BEFORE filemark You must explicitly move it past the filemark or subsequent reads will return 0, -1 or EOF w /dev/rmt/0b - BSD device name Tape head left positioned AFTER filemark Data is read/written from that point

18. Q Du Jour w What could happen if you mix AT&T and BSD tape device names when putting multiple backups on a tape? w What’s a “holey” file?

19. Holey Files Batman! w When a file says it is using more disk space than it actually is. w Output of du doesn’t equal what “ls -l” says. w Seeking way past the eof and writing data; no data exists between the old eof the new data. w Tar and cpio can be fooled into backup this empty space, dump/ufsdump can handle this oddity.