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AMANDA Under the Hood

AMANDA is a versatile tool that manages standard backup programs, optimizes schedules, and executes dump cycles efficiently, ensuring data protection. It comprises components like Planner, Driver, Dumper, and Taper, facilitating seamless backup operations.

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AMANDA Under the Hood

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  1. AMANDAUnder the Hood John R. Jackson Purdue University Computing Center jrj@purdue.edu

  2. Overview • Not a backup program itself • Manages other standard backup programs • System dump • GNU tar • smbtar • Optimized schedule • Dump cycle • Tape cycle • Estimated image sizes

  3. Overview(continued) tape driver planner driver taper driver dumper client holdingdisk sendsize sendbackup

  4. Planner • Get estimated image sizes • sendsize on client • Level 0 • Same level as last time • Next level • etimeout * number of disks • Analyze and pick initial level • Delay full dumps if total size too big • Promote full dumps if total size too small • Sort by “priority”, then size

  5. Strategy • standard • nofull • noinc • incronly • skip

  6. Driver • Gets sorted list from planner • Normal level • Degraded mode level • Starts one or more dumpers (inparallel) • Starts one taper

  7. Driver(continued) • Pick from beginning or end of queue? • Is it time to start this host? • Is it time to start this disk? • Is there enough bandwidth? • Is there enough holding disk space? • Is use of a holding disk allowed? • Are we below the client maxdumps limit? • Is this a different spindle?

  8. Dumper • Start sendbackup on client • Messages port • Data port (possibly encrypted) • Index port (optional) • Insert server side compression if requested • If “FILE-DUMP”: • Write tape header to holding disk chunk • Write data stream to holding disk chunk • Request new holding disk chunks from driver as needed • Else (“PORT-DUMP”): • Pass image to taper via localhost TCP connection

  9. Sendbackup msgs data index compression restoreprogram sendbackup stderr stdout backupprogram /dev/null stdin

  10. Taper • Run tape changer • Validate proper tape is mounted and rewrite label • Handle FILE-WRITE and PORT-WRITE commands • Write image to tape in 32 Kbyte chunks • Fail or advance to next tape on error

  11. Taper(continued) • Split into reader and writer • Shared memory buffer (e.g. 20 * 32 Kbytes) • Writer waits for all buffers full (or done) • Writer outputs as fast as possible for streaming • On error: • Advance to next tape if changer • Driver starts whole image over again

  12. Amandad • UDP for now • Client has no access to amanda.conf • Security checks • Run requested “service” • selfcheck • sendsize • sendbackup

  13. Files • Curinfo • Tapelist 200000525 B00116 reuse 200000524 B00115 reuse … • log.<YYYYMMDD>.<n> • Updated by driver, dumper and taper • Used by amreport to generate E-mail • amdump.<n> • detailed status • stdout/stderr from all programs • used by amstatus • /tmp/amanda/*.debug

  14. Administrative Tools • amcheck • amdump • amflush • amadmin • amstatus • amplot • amverify

  15. Administrative Tools(continued) • amtoc • amlabel • amrmtape • amtape • amcleanup • amreport

  16. Tape Format Label Tapemark Header Image Tapemark Header Image …

  17. Tape Format(continued) • No rewind!!! • System-V access method, not BSD • Tape label AMANDA: TAPESTART DATE 20000525 TAPE B00116 • Image header AMANDA: FILE 20000525 fortress.cc.purdue.edu / lev 1 comp N program /usr/sbin/ufsdump To restore, position tape at start of file and run: dd if=<tape> bs=32k skip=1 | /usr/sbin/ufsrestore –f… -

  18. Amrestore • Takes host, disk and datestamp patterns • Scans for all or first match • Usually gives back image ready for restore • Does not use any other AMANDA information

  19. Amrecover • Runs on client • Talks to amindexd on server to get file data • Talks to amidxtaped on tape host to read images • FTP-like interface and protocol

  20. Typical Problems • Check/Estimate/Data timeouts • Access not allowed • Host down • Disk offline • I/O error • port NN not secure • Broken pipe

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