Backup - Defense Against All Hazards





Nothing is so devistating to a business as a major data loss. When it happens, going out of business is not possible, it is probable. Maybe immediately, maybe in a year or so.

Adequate backup procedures are a pain in the butt, but if they are not followed properly, the pain could be in a much wider area of the anatomy.

Adequate backup devices can cost more than the computer they are mounted in, and they're cranky, failure prone devices too - but that cost looks very small indeed if you face rebuilding an information system with no current backup.

Think of backup as you would insurance. Insurance is a rip-off and big waste of money because nothing's ever going to happen, but when it does happen, you sure are glad you have insurance, aren't you?

  • Data Backup - Essential methods and devices.
    • Rules
    • Devices
    • Horror Stories - why backups fail.
  • Raid - Assuring uptime in the face of disk failures.
  • Power Backup - Why it is essential
  • Clustering - Assuring uptime when servers fail


  1. Verify: A backup that is not verified is not a backup. Verify radability after every backup (real backup software does this automatically). Frequently verify that the backup is backing up everything that needs to be backed up.

  2. No Media Changes: Use a backup medium that can hold the entire backup. If a media change is required during the backup, a "convenient time" to do backup just never happens. This requirement usually dictates tape as the backup medium.

  3. Responsibility: One person must be responsible for backup, and must understand that if backups aren't good, they'd better have one hell of a good reason (or a new job lined up). Someone else should occassionally check the backups jsut to be sure.

  4. Close All Files: All users must be logged out of programs during the backup run. All client server database managers must be closed. Check the logs to make sure nothing is preventing critical files from being backed up. If you cannot meet this condition, an open file backup manager such as St Bernard must be used.

  5. Layered and Rotated: Backups must be layered, and tapes must be rotated in strict order with every backup. The reason for rotation is that damage to a data file may not be discovered for days, and if all your tapes have backups in the damaged state, restoring does you little good.

  6. Full Backups Preferred: Incremental backups take more discipline to maintain properly than is available in most small businesses. Larger shops with lots of data have to use incremental backup because of time restraints, so they need to develop the requried discipline. Small shops with inadequate media have to do incremental backups or backups won't be made at all.

Common Backup Devices

These are typical of backup units in use today. Prices shown are budgetary and may vary in either direction. Cost of backup software is not included, but can range from "included with drive" to well beyond $700 depending on the needs of your business.

Rotating drives are sized uncompressed, since most backups to them are file by file. Real backup software can about double capacity depending on the nature of the files backed up. Tape drives are sized compressed as that is the way they are normally used. Capacity uncompressed is about half depending on the nature of the files backed up. SCSI tape drives have hardware compression and must be jumpered compressed or not compressed.

All listed items (except multi-tape changers) are internal. External units usually cost about $100 more.

  • Floppy Disks: Never very practical, now almost usless as not much will fit on them with today's bloated file formats.
    Capacity: 1.44-Meg
    Speed/Reliability Poor/Poor
    Cost Drive/Media $20.00/$0.50

  • Iomega Zip Disk: Much used for file transfer as a larger replacement for floppy disks, the Zip Disk is far too small to back up today's hard disks.
    Capacity:100-Meg, 250-Meg
    Speed/Reliability Poor (parallel) to Acceptable (SCSI, IDE) / Marginal
    Cost 100-Meg Drive/Media: $120 / $12
    Cost 250-Meg Drive/Media: $170 / $20

  • Writable CD-ROM: Reasonable capacity for partial backups and archival storage. Both Write Once and Rewritable versions are used. Drives have become common and affordable. Write Once disk can be read in almost all CD-ROM drives, Read/Write disks only in Read/Write drives meeting the same specification.
    Speed/Reliability Poor / Good
    Cost Drive/Media: $260 / $1.20 (WO) 4.00 (R/W)

  • DVD-RAM: Writable DVDs are still enmeshed in standards conflicts, so the media must be considered non-transferrable. You could get stuck with a library of disks, an dead drive, and no ability to replace it with a compatible unit.
    Capacity: 2.6-Gig (single side), 5.2-Gig (double side)
    Speed/Reliability Poor / Acceptable
    Cost Drive/Media: $575 / $22 (single side) $38 (double side)

  • Iomega Jaz Drive: Removable hard disk concept. Fast and reasonable capacity, but total media destruction happens a bit more often than we feel comfortable with.
    Capacity: 2-Gig
    Speed/Reliability: Very Good / Questionable
    Cost Drive/Media: $340 / $120
    Cost SCSI Controller:$85

  • Travan Tape (TR-4, TR-5): This is your basic low end tape drive today. It is available with an EIDE interface, so no separate controller is needed.
    Capacity: 8-Gig (compressed), 20-Gig (compressed)
    Speed/Reliability 1 to 2 Megabits/sec / Acceptable
    Cost 8-Gig TR-4 Drive/Media $250 / $34
    Cost 20-Gig TR-5 Drive/Media $360 / $42

  • Travan NS Tape (NS-8 NS-20): This is a higher grade version of Travan tape. Interface is always SCSI and the drive does write integrity testing as it goes and uses hardware compression.
    Capacity: 8-Gig (compressed), 20-Gig (compressed)
    Speed/Reliability 1 to 2 Megabits/sec / Good
    Cost 8-Gig NS-8 Drive/Media: $440 / $36
    Cost 20-Gig NS-20 Drive/Media: $540 / $45

  • DAT (Digital Audio Tape): The standard for small servers. DAT jukeboxes extend the media to large storage requirements. Inexpensive media, hardware compression, SCSI interface, helical scan machanism, and a wide range of prices depending on speed and capacity.
    Capacity: 8-Gig, 24-Gig, 40-Gig (all compressed)
    Speed/Reliability: 1.1 to 5.0 Megabytes/sec / Very Good
    Cost 8-Gig Drive/Media: $620 to $850 / $10
    Cost 24-Gig Drive/Media: $850 to $1300 / $18
    Cost 40-Gig Drive/Media: $1220 to $1600 / $44
    Cost SCSI Controller: $60
    Cost Cleaning Cart: $16

  • VXA Tape Attractive price, high speed and extremely reliable media. The downside is it is a single vendor solution (Ecrix).
    Capacity: 12-Gig, 33-Gig (same drive, different media)
    Speed/Reliability: / Very High
    Cost Drive/Media: $799 / $29 (12-Gig) $79 (33-Gig)
    Cost SCSI Ctrlr: $60
    Cost Cleaning Cart: $35

  • SLR (QIC Cartridge) SLR is the successor to the QIC cartridge that was long the standard for small servers and Unix boxes (starting at a huge (for its day) 30-Megs). Fast, sturdy mechanism (compared to DAT), reliable, long tape life.
    Capacity: 24-Gig, 32-Gig, 50-Gig
    Speed/Reliability 2.4 to 4.0 Megabytes/sec / Very High
    Cost 24-Gig 2.4-Meg/min Drive/Media: $1060 / $56
    Cost 32-Gig 3-Meg/min Drive/Media: $1290 / $66
    Cost 50-Gig 4-Meg/min Drive/Media: $1890 / $89
    Cost 500-Gig 1dr Chgr. Drive/Media: $10,200 / $89
    Cost 1000-Gig 1dr Chgr. Drive/Media:$19,500 / $89
    Cost 1000-Gig 4dr Chgr. Drive/Media: $27,500 / $89
    Cost SCSI Controller: $60 to $250
    Cost Cleaning Cart: $40

  • DLT (Digital Linear Tape): "Screaming Tape" - long the standard for high end servers requiring very fast backup. Highly reliable
    Capacity: 40-Gig,
    Speed/Reliabilty 10-Gig/hr 40-Gig/hr / Very High
    Cost 40-Gig 10-Gig/hour Drive/Media: $2700 / $50
    Cost 70-Gig 36-Gig/hour Drive/Media: $4750 /
    Cost 80-Gig 40-Gig/hour Drive/Media: $5300 /
    Cost 280-Gig Chgr. 5-Gig/hour Drive/Media: $5700 /
    Cost 480-Gig Chgr. 5-Gig/hour Drive/Media: $8700 /
    Cost SCSI Controller: $200
    Cost Cleaning Cart: $40

  • AIT Tape: A new format provided by a number of vendors.
    Cost 70-Gig Drive/Media: $2100 / $122 (70-Gig) $104 (50-Gig)
    Cost 100-Gig Drive/Media:$4400 / $130
    Cost 200-Gig 1dr Chgr. Drive/Media: $5100 / $104
    Cost SCSI Controller $60 to $250
    Cost Cleaning Cart: $57

Rotation Schemes

  • There must be an archive backup (preferably two used in rotation) that is updated only periodically and after each major reconfiguration. These archive tapes should be stored well away from the regular backups.
  • The daily backups rotation set for the smallest business with data that isn't that critical, three tapes, minimum.
  • For a larger business or for more critical data, the rotation set should be a week deep. There should be a tape for every day of the week, rotated every day in strict order.
  • If at all possible, the most recent tape should be rotated off site every day.
  • For very critical data there should also be a weekly rotation set of 5 tapes. Every Friday tape, as soon as it is removed from the backup drive, should be swapped out for the Friday tape corresponding to the same numbered week in the weekly set. This gives you a month deep backup rotation set.

©:Andrew Grygus - Automation Access -
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