BACKUP/MASTER: Immediate Relief with Disk Backup

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BACKUP/MASTERImmediate Relief with Disk Backup
Presented by W. Curtis Preston VP, Service
Development GlassHouse Technologies, Inc
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Tape backups are taking too long

• High-speed tape drives in a library are the
  standard, but the cost of these units causes many
  people to cut corners elsewhere
• The nature of tape drives also creates difficulty
  when creating offsite tapes
• Many people arent utilizing the tape drives
  properly and are not getting all their backups
  done
• Also, many are not creating offsite copies
• Stand-alone tape drives must be swapped

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Tape drives The advantages

• High-speed, low cost
• Good archival solution. Allows multiple copies
  without significant cost.
• Lots of new tape drives on the market
• 9940B (30/70 MB/s)
• AIT-3 (15/30 MB/s)
• LTO (15/30 MB/s)
• Super DLT (11/22 MB/s)

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Tape The challenges

• Tapes are now too fast!
• Must use multiplexing to stream them during
  network backups
• Must use higher multiplexing values than ever
  before, hurting restore performance more
• Tape-to-tape copying takes time, and multiplexing
  increases that time especially if you
  de-multiplex
• Must perform regular full backups to reduce
  number of tapes required for restore
• Incremental backups do not supply enough data to
  stream a tape drive

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Tape The challenges (2)

• Cannot write to single tape drive from two shared
  servers simultaneously
• Single tape can cause large restore to fail
• You never know if a tape is good until you really
  need it

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Still not making offsite copies

• Assuming copy is same speed as backup, must buy
  at least twice as many drives to perform copies
  in one day
• If copy is not same speed, must accept longer
  copy window or buy more tape drives
• Additional drives cost a lot of money
• Result Many people still not making offsite
  copies

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Solution New backup media

• Really inexpensive disk arrays
• IDE/ATA-based
• Addressable via Fibre Channel, SCSI, Firewire,
  NFS, or CIFS
• JBOD and RAID configurations (Use their RAID
  controller or a software volume manager.)
• As low as 5,000 per TB for off-shelf units,
  2,000 for build-your-own units!

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What to do with them?

• Buy enough disk for two full backups and many,
  many incremental backups
• Connect array to clients or backup servers via
  Fibre Channel SANs, or GbE NFS/CIFS

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What to do with them? (2)

• Back up to disk first using your backup software
  of choice
• Duplicate disk backups to tape
• Except in disaster, restores come from disk
• Maybe place (another?) disk unit offsite and
  replicate to it

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What to do with them? (3)

• Most backup products do things that are not
  necessary when backing up to disk
• Occasional full backups
• Backing up redundant files
• Incremental backups of entire files
• New products designed to back up to disk
• Forever incremental w/o performance hit
• Some even eliminate redundant blocks across hosts

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What to do with them? (4)

• Replicate many clients to a central array, back
  up that array using backup software, and
  duplicate to tape for offsite copies
• Allows you to use replication without the cost of
  traditional RAID arrays

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What to do with them? (5)

• Could also use software-based RAID to create
  additional mirror, and split mirror for backups
• Gives you BCV functionality for ¼ the price!
• Back up large databases with no I/O overhead on
  server!

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Why would you do that?

• Dont require constant stream
• No need to multiplex on most disk devices
• Depending on implementation, multiplexed backups
  may still be faster on disk
• If you did multiplex your disk backups, you could
  easily de-multiplex the tape copies with no
  performance penalty
• NFS/CIFS devices can be used simultaneously by
  many clients, without needing to stream each
  device

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Why would you do that? (2)

• Incremental backups with little data will not
  hurt performance of other backups
• Protected via monitored RAID -- the loss of a
  single disk would be monitored and repaired,
  while the RAID group continued to protect the
  data
• Disk-to-tape copies are easier than tape-to-tape
  copies
• Could perform infrequent full backups without
  increasing the chance of failure
• Full backups can be performed less often, saving
  networks and CPU utilization

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Why not back up everything to disk?

• Archiving purpose of backups requires older
  backups to be available
• Tapes still much cheaper, allowing for multiple,
  stable copies to be put on the shelf onsite or
  offsite
• Tapes not susceptible to filesystem corruption

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Issues

• Staging process needs automation
• Need to automatically move data from disk to tape
  without removing from disk
• Should allow you to leave backups on disk ALAP,
  and automate moving data to tape when necessary
  (policy-based, not just retention-based.)
• Increase ease of recovery
• Need to be able to import disk images
• Creation of a Synthetic Full would be very nice
• Backup twinning should be able to go to disk and
  tape

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In Short

• Doing backups to inexpensive disk first allows
  for
• Faster, easier backups especially incremental
  backups
• Easier creation of offsite tapes
• Easier restores both on- and offsite
• Many other features
• A directory of ATA Fibre SCSI addressable
  arrays is available at
• http//www.storagemountain.com
• Questions to cpreston_at_glasshouse.com