backup & restore the purpose of backup is to protect data from loss. the purpose of restore is...

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.

Backup

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

• Implementation

• Inventory (content and media)

• Verify

• Automate

• Secure

Factors

• Determine which data is critical.

• Determine frequency and types of backups to be used.– Full– Differential– Incremental

Factors

• Determine which data is static and which is dynamic.– 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

Factors

• Determine the appropriate media storage for your backups:– CD– DVD– Tape– Disk– Solid State?

Factors

• Partitioning of disk space is used to manage backups

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

Schedule

• Determine the categories of data so you can schedule the backups accordingly

Schedule

• 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).

Schedule

• Full Archival Backup– image backup implies copying the unused

space.

• 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 duplicated.

• Many full backups ignore empty space.

Full Archival Backup (Pros)

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)

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 subpoenaed.

• Statute may require destruction of some records.

Differential Backup

• Copy files changed since the last full backup.

• Differential backups grow with time. They can eventually grow larger than the last full backup.

• 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

files– 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 backup

• 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

hardware– Not everyone archives the local “C-Drive” on

general purpose workstations. (SLA and user awareness)

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

Verify

• The only time you know the quality of your backup media is when you are doing a restore.

• This is the worse time to discover you have problems.

• 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 scheduling

• 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 admin.

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

encryption

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

backup?– 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

offsite.

Data Compression

• Risks – if the media is damaged, recovery may be difficult or impossible.

• Lossy – some data tolerates degradation (loss of

information)

• 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.

Restore

• 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 backup).

• 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.

Tapes

• Tape historically has been the preferred backup media for very large data storage environments.

• Tape has a useful life span.

• Tape can be very robust for storage

• Easy to transport

• Some tape formats are more reliable than others.

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 itself.

• 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.

Tape

• Rotate media– Incremental backup stored on site can be

reused.

Tape Standards

• 8mm

• DLT

• DAT (4mm)

• QIC

• http://www.pctechguide.com/15tape.htm

• Imation.com

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.

Firedrills

• An occasional test of a full partition restore is not unreasonable. This would be done if– A change is made in the backup software

release.– A change of vendor for the backup software

product.– When a new server with new unused disk

arrives.

Centralization

• 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 solution.

• RAID 1+1, includes a second mirror in a RAID 1 array.

Technology

• 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