BACKING UP LINUX SYSTEMS

A talk for Linux Users of Victoria - Peter Warren, 4 June 1996.

Excuses for not backing up
Motivation for backing up
Developing a Strategy
Hardware
Software
Conclusion
Hotswapping IDE Disks under Linux

References:

• A description of a backup system using ordinary hard disks can be found in: hd_backup_system.txt
• Discussion and development of hotswapping of IDE drives can be found in: ide_hotswap.txt

EXCUSES FOR NOT BACKING UP

• Too much effort
• Too expensive
• Inconvenient to do
• Specs on HD say 300,000 hours MTBF. That's 34 years...
• It's all there on the distribution CD
• Rationalization - it's a good risk

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if ( FEAR > (Procrastination +
             Inconvenience +
             Cost +
             Effort + ...)) {

   BACKUP = TRUE;
}

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DEVELOPING A STRATEGY

• Identify risks
• What's worth backing up?
• General requirements
• Final Specification

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IDENTIFY RISKS

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WHAT'S WORTH BACKING UP?

    ____________
    |          |
 ___|____   ___|____
 | AZUL |   |INDIGO|  Internet
 |______|   |______|--->

DOS   200Mb  News  300Mb
Linux 400Mb  Linux 400Mb

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GENERAL REQUIREMENTS

• KISS
• Low cost Fast - convenient
• Reliable
• Generic - minimum of proprietary hw/sw

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FINAL SPECIFICATION

• Full backup of 2 Linux systems - 800 Mb
• Cost: < $800
• Copies: minimum of two
• Must work with current stable kernel
• Backup time: < 2 hours total

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HARDWARE

• Tapes
  • Floppy streamers
  • IDE tape drives
  • DAT tape drives
• Removable Hard Disks
  • Iomega - Zip, Jaz
  • Syquest - 135, 270, (SyJet 1.3Gb)
• Other
  • Ordinary hard disks

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FLOPPY STREAMERS

• PROS
  • Cheap - $350 plus $30/tape
  • Good Linux support
  • Good generic tape standards
• CONS
  • Slow
  • Limited capacity
  • Inherent fickleness of tapes
  • Can't use floppy drive at same time

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IDE TAPE DRIVES

• PROS
  • Much faster that floppy streamers
  • Good capacity - (2Gb native)
  • Uses generic IDE interface
• CONS
  • More expensive - $1000 plus $40/tape
  • Inherent fickleness of tapes
  • Only beta support in dev kernel

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DAT TAPE DRIVES

• PROS
  • Fast
  • High capacity
  • Uses generic SCSI interface - good Linux support
• CONS
  • Expensive - $1700 plus $40/tape
  • Extra cost of SCSI card

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IOMEGA - ZIP AND JAZ DRIVES

• Zip
  • Capacity: 100Mb
  • Cost: $300 plus $30/cartridge
  • Interface: SCSI and Parallel port
• Jaz
  • Capacity: 1Gb
  • Cost: $970 plus $240/cartridge (US street prices: $US490 + $US125)
  • Interface: SCSI only

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SYQUEST - 135, 270, SYJET 1.3GB

• 135, 270
  • Capacity: 135Mb, 270Mb
  • Cost: $530 plus $100/cartridge
  • Interface: SCSI and IDE
• SyJet 1.3Gb
  • Cost: $900 plus $195/cartridge
  • US rrp: $US500 + $US95)
  • Interface: SCSI and IDE
  • Avail Australia: Aug 1996

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ORDINARY HARD DISKS

• PROS
  • Cheap (compared with removable disks). 1.2Gb $250
  • Faster and more reliable than tapes
  • Simple, flexible, generic
• CONS
  • Not designed to be "removable"
  • Bulkier and more fragile than tapes and removable disks

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SOFTWARE

• Basic tools
  • tar, cpio, afio
• Floppy streamer drivers
  • ftape, zftape
• Backup packages
  • KBackup, taper
• Commercial packages
  • Bru

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CONCLUSION

Use ordinary hard disks with a removable disk cassette kit, plus basic software tools

• Cost: 2x1.2Gb drives plus 2xdisk cassette kits = $660
• Allows 2 full backups uncompressed (4 compressed)
• Backup time: 40 mins (uncompressed tar 1Gb)
• Simplest solution
• No proprietary components

• Only significant drawback: bringing the system down to insert/remove the disk

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HOTSWAPPING IDE DRIVES UNDER LINUX

Issues

• CMOS settings
• Master/slave jumpers
• Booting without drive present
• Recognizing drive when it is attached
• Electrical connection of drive to running system. Making 5V, 12V and 40 pin connections so drive is not damaged.

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