Backup _ Restore by yaofenjin


									          Backup & Restore
• The purpose of backup is to protect data
  from loss.
• The purpose of restore is to recover data
  that is temporarily unavailable due to some
  unexpected event.
To backup or not to back up, that is the question.
– Backup is not free.
– No backup is risky.
       Proper Backup Procedure
•   Choose your application
•   Scheduling
•   The actual backup
•   Inventory (content and media)
•   Verify
•   Automate
•   Secure
• Determine which data is critical.
• Determine frequency and types of backups
  to be used.
  – Full
  – Differential
  – Incremental
• Determine which data is static and which is
  – Some OS installations are changed
    infrequently; few backups required
  – E-commerce may require continuous backups.
  – Understand the changing state of your client’s
    data to determine an appropriate backup sched.
  – Organize with partitions
• Determine the appropriate media storage for
  your backups:
  –   CD
  –   DVD
  –   Tape
  –   Disk
  –   Solid State?
• Partitioning of disk space is used to manage
     Choose your Backup App
• Mac OS X :
  – Time Machine
• Linux/Unix :
  – tar (tape archive), cpio, dump
• MS Windows :
  – MS Windows XP & 7 includes Backup &
    Restore capability
  – Many commercial apps are available
 Enterprise Level Backup Apps
• Paragon Backup & Recovery includes
  customer support
• Backup4All Professional
• GRBackPro7
• Determine the categories of data so you can
  schedule the backups accordingly
• Partitions are often used to manage backups
• Examples:
  – The OS has its own partition and may require
    infrequent backups if changes are quarterly
  – User data may require nightly backups
  – Users must know what partitions have backup
    and the frequency (SLA).
• Full Archival Backup
  – image backup implies copying the unused
• Differential Backup – what has changed
  since the last backup
• Incremental Backup – what has changed
  since the last backup of anytype
        Full Archival Backup
• Mirror – every last bit on the disk is
• Many full backups ignore empty space.
   Full Archival Backup (Pros)
• Provides a complete copy of data
• Easy to manage:
  – Done less frequently than other types of
    backups due to cost and resource requirements:
    Monthly, Quarterly, semi-annually, annually.
   Full Archival Backup (Cons)
• Usually requires more media space than
  either differential or incremental.
• Takes a long time to recover the full backup
  to a new disk.
          Full Archival Backup
• Consider making multiple backup copies
• Full backup media should be stored offsite to
  protect data from disasters
   – Fire, Flood, Earthquake, Terrorist attack, Sabotage,
     Hacker attacks
        Full Archival Backups
• The trend is to reduce the cycle of full
  backups. This is because of liability. Files
  that are not backed up cannot be
• Statute may require destruction of some
         Differential Backup
• Copy files changed since the last full
• Differential backups grow with time. They
  can eventually grow larger than the last full
• Scheduled less frequently than a full
  backups: Weekly, monthly.
     Differential Backup (Pros)
• Redundancy
• Usually takes up less time and space than a
  full backup.
• If the differential backup grows to the size
  of the last full backup, then schedule a new
  full backup.
    Differential Backup (Cons)
• Redundancy – potentially many unneeded
  copies of the same data.
• Subsequent differentials take longer and use
  more media space.
        Incremental Backups
• A backup of what has changed since the last
  previous backup of any type.
• Frequency of incremental backups depends
  on the client needs.
  – Weekly, daily, hourly, continuously.
         Incremental Backups
• Pros
  – Keeps a revision history of actively changing
  – Fastest backup type
  – Uses the least amount of media to complete a
    single backup
• Cons
  – Much more difficult to manage
          Schedule Example
• Full backup twice per year
• Differential each first Saturday morning of
  each month that is not scheduled for a full
• Incremental each Saturday morning that is
  not scheduled for a Full or Differential
 Other Schedule Considerations
• Consider completing a backup in
  conjunction with and before any major
  system changes are scheduled.
          The Actual Backup

• Assignment of responsibilities
  – Written in the SA’s job description
• Acceptance of accountability
  – A signed form indicating that the backup was
    complete, verified and secured
         The Actual Backup
• Hardware
  – Choose the media type
  – Centralize the backup to reduce redundancy of
  – Not everyone archives the local “C-Drive” on
    general purpose workstations. (SLA and user
           Backup Inventory
• Inventory the backup media
  – Tapes and other writable media use barcodes or
    hand-written labels
• Inventory the content of the media
  – The backup should have a table of contents
    included in the backup
             Backup Inventory
• The media label information:
  –   Date
  –   System identifier
  –   Partition name(s)
  –   Backup category: full, differential, incremental
• The only time you know the quality of your
  backup media is when you are doing a
• This is the worse time to discover you have
• Restore a small subset of random files from
  the backup. Verify their integrity through
  differences or checksums.
          Verify: Firedrills
• When new equipment arrives, test your
  backup procedure on the new equipment to
  verify it works correctly
        Backup Automation

• Automation reduces human errors.
• Many pre-packaged apps include automatic
• Linux/Unix backup scripts can be submitted
  using the cron utility. Logs can be kept in
  /var/log, and e-mail can be sent to the
         Secure The Backup
• Offsite storage
• Encryption: to encrypt or not to encrypt, …
  – Will the encryption key always be available?
  – Statute or contract (SLA) may require
      Secure: Off-Site Storage
Off site storage has risks all its own
  – Data can be lost/destroyed in transit
  – How important is it to have a backup of the
  – Some backups can be kept on site
     Secure: Example Strategy
Where the backup is stored will impact
 service response to restore requests:
  – Consider keeping incremental backups on site.
  – Differential and full backups could be stored
            Data Compression
• Risks – if the media is damaged, recovery
  may be difficult or impossible.
• Lossy
  – some data tolerates degradation (loss of
• No-loss
  – Some data should not be compressed. Know
    your data!
            Secure Backups
• Contract to store your data in a “secret”
  offsite location. (Secret implies a need to
  know basis)
       Backup Considerations
• Backups slow down service. This should be
  included in the SLA
  – Files should be write-locked during backup.
• Avoid doing backups during peak service
  hours. Schedule during early AM hours on
  the weekend and holidays.
• Common reasons for restores
  – Accidental file deletion
  – Disk failure
  – Disaster recovery
     • Fire, flood, earthquake, hacker attack, sabotage,
       terrorist attack, etc.
       Accidental File Deletion
• If backups are once per day, lost work is limited to
  one day for a given file. (RAID does not help)
• As storage technology gets cheaper by the Gbyte,
  it becomes easier to implement more sophisticated
  storage procedures that are more timely. (HDD
• A user wants the restoration to be immediate. The
  quicker the turnaround, the happier your customer.
                  Disk Failure
• A disk failure causes two problems
   – Loss of data
   – Loss of service
• Critical systems should implement RAID so that
  disk failures do not cause a loss of service.
• Restoring an entire disk is slow. Service is
  hampered until the last bit is recovered.
   – Consider using hot spares and hot swap
      Disk Restore from Tape
• Restoring from tape can interrupt service.
• Restoring from tape slows the restore
  process by a factor of about 5-10 times
  compared to a simple disk to disk copy.
               Tape Backup
• Large amounts of data historically favored
  tape media for backup:
  – Tapes are portable and fairly durable.
• Tape historically has been the preferred
  backup media for very large data storage
• Tape has a useful life span.
• Tape can be very robust for storage
• Easy to transport
• Some tape formats are more reliable than
             Tape Inventory
• Backup tapes must be
  – Properly labeled
  – Properly stored
• Proper inventory is needed to do restores in
  a timely fashion.
  – Hand written labels are ok
  – Bar codes and printed labels are better.
             Tape Inventory
• Inventory is not limited to the physical tape
• The contents of tapes must be inventoried.
• The number of accesses must be logged
  because tapes ware out.

  – Tape equipment is not free. You don’t want to
    purchase any more hardware than is needed.
• Rotate media
  – Incremental backup stored on site can be
             Tape Standards
•   8mm
•   DLT
•   DAT (4mm)
•   QIC
          Tape Technology
• Tape technology expands in leaps.
• Tape hardware purchases are not made on a
  constant basis (like disk storage).
• Tape technology is purchased in leaps.
  Three year intervals are more practical.
• An occasional test of a full partition restore
  is not unreasonable. This would be done if
  – A change is made in the backup software
  – A change of vendor for the backup software
  – When a new server with new unused disk
• Without centralization, a tape drive is
  needed for each server location.
• Equipment can be interchanged more easily
  when centralized.
     High Access DB Backups
• Some data changes so rapidly that backups
  are not practical.
• RAID 1 mirroring may be the only practical
• RAID 1+1, includes a second mirror in a
  RAID 1 array.
• Disk space cost drops by 1/2 about every
  18-24 months.
• Disk space is filled as it expands.
• Disk requirements are increasing on a
  continuous basis.
• Disk budgets increase faster than tape
  backup budgets.
            Backup Procedure
•   Choose your application
•   Scheduling (know your data)
•   The actual backup
•   Inventory (content and media)
•   Verify
•   Automate
•   Secure

To top