Backup q Why backup m The choice of

Backup q Why backup? m The choice of goals. q Where? m The choice of medias. q What? m The choice of contents. q When? m The choice of schedules. q How? m The choice of procedures of operations. Backups 1

Backups q Unattended backups - Avoid manually switch the tapes for one backup if possible • Buy a higher-capacity tape device • By a stacker or library and feed multiple pieces of media to one device • Change you dump sequence • Write a smarter script • Use multiple backup devices q Protect your backups m Keep tapes off-site m Secure store Location m Write-locked q Limit activity during dumps Backups 2

Backups q Verify your backup tapes m List the contents m Restore to a another server q Develop a tape life cycle q Label your tapes • Uniquely identify their contents • Format, exact syntax of the dump command • Get a label machine q Pick a reasonable backup interval q Design your data for backups q Choose file systems carefully q Prepare for the worst q Perform centralized backup Backups 3

Backup Strategies q Full backup m Copy all the files on a system to a backup device m Time consuming q Incremental backups m Copy only those files that have been changed since some previous backup m Fast m Need previous backup for a complete restore q Backup level m Each backup type has a level number assigned to it. m Full backup is 0 m Backing up the system at level N means saving all the files that has changed since the very last backup at the level less than N Backups 4

Backup Strategies q Combination of using multiple levels: m Example 1: • Backup schedule: – Monday level 0 backup – Tuesday level 1 backup – Wednesday level 1 backup – Thursday level 1 backup – Friday level 1 backup • How many tapes are needed to restore the complete filesystem? Backups 5

Backup Strategies m Example 2: • Backup schedule: – First Monday of month level 0 full – All other Mondays level 1 weekly incremental to 0 – Tuesday level 2 daily incremental to 1 – Wednesday level 2 daily incremental to 1 – Thursday level 2 daily incremental to 1 – Friday level 2 backup • How many tapes are needed for a complete restore? Backups 6

Backup Strategies q Consider: m Use different schedule for different filesystems m Make a full backup whenever you make significant change • A new kernel • OS upgrade • New application package installation Backups 7

Backup Devices and Media q Use removable media q For media using magnetic particles, avoid m Audio speaker m Transformers and power supplies m Monitors use transformers and high voltages. m Prolonged exposure to the earth’s background radiation q Floppy disks m Cheap and short life m Small capacity and slow m Drive comes with the system Backups 8

Backup Devices and Media q Super floppies m Zip drive • More capacity ( > 128 MB) • High media cost • Available with parallel, serial, SCSI and USB connectors. q CD-R and CD-RW m More capacity, 650 MB m Available with SCSI, IDE, parallel, USB, etc. m Are written with a laser through a photochemical process – longer shelf life than magnetic media • Have you heard of CD-eating fungus? q DVD writer m High capacity Backups 9

Backup Devices and Media q Removable hard disks m Orb drive from Castlewood Industries, 2. 2 G m Jaz from Iomega, 2 G m Speed is attractive, comparable to normal disk drives m Small system and home machine backup q DDS(4 mm) cartridge tapes m Digital Data Storage m Use same principle as home video recorders – more reliable, lower error rate than DAT( Digital Audio Tape) m Can hold up to 20 G Backups 10

Backup Devices and Media q DLT (Digital Linear Tapes) m Popular backup device m Quantum m Hold large amounts of data: DLT 4 80 G m Fast transfer rate: 6 MB/s m Pricey media q AIT (Advanced Intelligent Tape) m 6 MB/s m 50 G q Mammoth m Exabyte’s m 12 MB/s native transfer rate Backups 11

Backup Devices and Media q Jukeboxes, stackers and tape libraries m A stackers is a simple tape changer that is used with a standard tape drive m A jukebox is a hardware device that can automatically change removable media in a limited number of drives m Tape libraries are a hardware backup solution for large data sets. q Hard disks m Backup over network q What to buy? m Budget m requirement Backups 12

Native Backup & Recovery Utilities q Backing up with the dump utility q Restoring with the restore utility q Backing up and restoring with the cpio utility q Backing up and restoring with tar utility q Backing up and restoring with dd utility q Device-level tape manipulation with mt Backups 13

Dump and restore q the most common way to create and restore from backups q The underlying commands used by automated backup software q Advantages: m Backup can span multiple tapes • It detects the end of tape (EOT) and ask for a new tape m m m Files of any type (even devices) can be backup and restored Permissions, ownerships and modification times are preserved. Files with holes are handled correctly Backup can be performed incrementally Read the inode table, so very efficient. Long names are handled correctly. Backups 14

Dump and restore q Limitations m Every filesystems must be dumped individually m Only filesystems on the local machine can be dumped. q Incremental backup m File /etc/dumpdates to determine how far back an incremental dump must go m Flag u causes dump to automatically update /etc/dumpdates must be created manually first time m Dump sends output to some default device unless flag f is used • Use nonrewinding tape when put multiple dumps on a single tape. Backups 15

Dump and restore q Dump’s most important options m 0 -9 The first argument of dump is the incremental dump level. mu Update /etc/dumpdates upon successful backup ms The size of the backup tape in feet md density of the backup tape in bytes per inch (bpi) q Example: m $ dump 3 u /chem Backups 16

Dump and restore q Restore’s most important options m r Read and restore the entire tape m x extract all files and directories listed and restore them in the current directory m t type the name of the listed files and directories on the terminal. Can be used to verify the tape is readable. m f name of the file or device holding the dump m s the corresponding argument indicates which file on tape is to be used for the restore. m i interactive mode. Most useful to restore a small group of files. Backups 17

Dump and restore q Restore a entire filesystem m Step 1: resotre the most recent level 0 dump m Step 2: restore the recent next level m Step 3: continue the procedure step 2 until the last dump m Example: • Some dump sequences. Red number are the ones need to restore. – 000000 – 032545 Backups 18

Dump and restore m. A complete example: #/etc/mount /dev/dsk/c 201 d 6 s 0 /home #cd /home Mount first tape of level 0. Use mt to position to the right spot and then #restore r Mount the next level tape. Use mt to position to the right spot and then #restore r Backups 19

Dump and restore q Again, exact command name, options, syntax varies from platform to platform m Example, On Solaris • dump has nothing to do with backup • The dump command is ufsdump • The restore command is ufsrestore m Check the OS specific document before you type the command Backups 20

tar q An archiving program for store and extract files from an archive file known as tarfile. q Features: m m m m create (-c), extract(-x) or view (-t) a tape file Tarfile can be on tape file or a normal file (-f). Recursive to directory preserves ownership information (-p option) Follow symbolic link (-h option) Blocking factor may yield better performance (-b) Use relative path (-C) q Drawbacks of some version of tars m May not allow multiple tape volumes m Pathname may be limited to 100 m File size maybe limited to 2 G Backups 21

tar q Format: m %tar options list_of_files q Examples: m Save all files under /home to the default tape drive. $tar –c /home m Copy directory tree fromdir to todir $tar cf – fromdir | (cd todir; tar xfp - ) m Save all the files under the directories /home, /home 2 and /checm/public • $tar –cf /dev/rmt 1 /home 2 /chem/public m Perform a backup of files has been changed within a day • $ tar c `find /home –mtime – 1 ! –name ‘*. o’ ! –type d –print` Backups 22

cpio q Copy files to and from archives q Advantages m It is designed to easily backup completed arbitrary sets of files; tar is easiest to use with directory subtrees. • Work with find together. m m m It packs data on tape much more efficiently than tar. On restore, it skips over bad spots on the tape while tar just dies. It can span tapes. q Three operating modes m Copy-out mode (-o) • Read a list of filenames, one per line, on the standard input, and write the archive onto the standard output. • Example: $find /home –print |cpio –o > /dev/rmt 0 Backups 23

cpio m Copy-in mode • Copy files out of an archive or lists the archive contents m Copy-pass mode • Copy files from one directory tree to another, without using an archive. $find fromdir –depth –print | cpio –pdm todir m Perform an incremental backup using cpio $ touch /backup/home_full $ find /home –print | cpio –o > /dev/rmt 0 A day later … $touch /backup/home_incr_1 $find /home –newer /backup/home_full –print | cpio –o > /dev/rmt 0 Backups 24

dd q A file copying and conversion program m Transfer raw data between devices q Example: m Make a copy of magnetic tape $dd if=/dev/rmt 8 of=/dev/rmt 9 cbs=16 b If there is only one tape: $dd if=/dev/rmt 8 of=tfile cbs=16 b $dd if=tfile of=/dev/rmt 8 cbs=16 b m Convert the byte order, a usage to read on a SUN machine a tar tape written on an SGI machine: $ dd if=/dev/rst 8 conv=swab | tar xf Backups 25

mt q Direct manipulation of tapes q Format: mt [-f tapename] command [count] q Commonly used function m Remind (rew) m Check status (status) m Puts the tape off-line (offl) m Position a tape at a particular fileset (fsf [count], bsf [count]) • Can be confusing • Quite useful sometime q Example m Find what’s on a tape with no labels Backups 26

Commercial Backup utilities q Consideration m Full support of your platforms - heterogerous m Backup of raw partitions m Multiplexing • Simultaneous backup of many clients to one drive • Simultaneous backup of one client to many drives m m m m m Storage management features Reduction in Network traffic Support of a standard or custom backup format Ease of administration Ease of recovery Protection of the backup index Automation Cost Vendor Backups 27

Commercial Backup utilities q Some packages with Unix vendor with extra payment q Enterprise level backup solution examples m Commercial software • Veritas Netbackup • HP Openview Omni. Back m Free software • Bacula • Amanda Backups 28

Backing Up and Restoring the System Filesystems q Backup/restore the modified configuration q When system filesystems need to be completely restored: m Reinstall OS and restore the files that you have modified • How many files have been customized • How widely they are spread • How much device and other reconfiguration needs to be redone m Booting from alternate media and then restoring the filesystems from full backup. • Basic steps – Bootoff media – Prepare the filesystems – Restore • DOCUMENT and TEST the procedure – Emergency boot tapes only has limited number of normal system commands Backups 29

Backing Up and Restoring the System Filesystems m Bootable backup tapes on some Unix versions • • • Created from live system Self-restoring Examples: – AIX’s mksysb utilties » It saves all of the filesystems in the root volume group ( /, /usr, /var, /home, /tmp, etc) # mkdyb –i /dev/rmt 0 » To restore , boot from mksysb tape » Can also serve as a way to clone a system » Can also be used as a regular backup tape. – HP-UX recovery tape » Run the command mk_recovery Backups 30

Tape Special Files q Tape drives often have names of m /dev/rmt. N or /dev/rmt/N • Where N indicates the drive number m Include other characters as suffixes or prefixed to indicate • • The density setting Hardware compression setting Rewinding setting For example: – /dev/rmt/0 mn Backups 31

Moving data between systems q In general, tar, cpio and dump archives are readable on many systems. But, m Block size difference m Archive format incompatibilities m Byte order difference m Compressed archives Backups 32

Remote backup and restores q Why remote? m No local tape drive m Faster tape drive on another system q Command rdump and rrestore m The device name is • Host: local_device • #rdump 0 uf anchor: /dev/nst 0 /spare m Permission control • . rhosts Backups 33

Database Backup & Recovery q Database can be build on m Raw device m Unix files q Database backup can be m Offline • No access to database at all. • Regular raw device/unix file backup can be applied m Online • Database is available to end users – On going transactions – modification to multiple devices/files with one transaction • Data integrity – Transaction log – Special backup commands/configuration Backups 34

Database Backup & Recovery q Example: m Sybase m. Transaction log m. Dump tape definition (size, device filename ) inside the db m. Dump command m. Support multiple volume m. Has to wait until tape is ready m. Use non rewinding tape for multiple database. m. Recovery is straight forward Backups 35

Database Backup & Recovery q Example: m Oracle • Cold backup – shutting database down. – Incremental at filesystem level does not work – Recovery is ready. m Hotbackup – turn on Archive mode m Archive log/undo log/redo log m Recover upto the point of failure m Backup mode m File system backup m RMAN ( Support incremental) m Hot backup Recovery is a headache Backups 36

Summary q Backup is important, don’t neglect it m Strategy m Monitor m Test Backups 37