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.

Factors of a Proper Backup

• Planning• Scheduling• Backup operation• Inventory (content and media)• Verification• Automation• Security

Planning

• Choose your backup app.• Determine which data is critical.• Determine frequency and types of backups

to be used.– Archival (mirror or image)– Differential– Incremental

Planning

• Determine which data is static and which is dynamic.– The OS and apps tend to be static; few backups

required– E-commerce transactions may require continuous

backups.– Understand the changing state of your client’s data

to determine an appropriate backup sched.– Organize with partitions

Planning

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

Schedule

• Full Archival Backup– Mirror backup– image backup

• Differential Backup• Incremental Backup

Full Archival Backup

• Formatted into a single file and stored on your media choice.– Mirror– every last bit on the disk is duplicated

including empty space.– Image - empty space is ignored

Full Archival Backup (Pros)

Pros• Provides a complete copy of data• Easy to manage:

– Done less frequently than other types of backups :

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:– Fire– Natural disasters (flood, earthquake, etc)– Terrorist attack– Sabotage– Hacker attacks

Archival Addendum

• Files that are not backed up cannot be subpoenaed.

Differential Backup

• Copy the 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 (also a potential pro)

• 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

• Cons– Much more difficult to manage

Backup Inventory

• Inventory the backup media– Tapes and other writable media use barcodes

and labels• Inventory the content of the media

– The backup may require a table of contents

Verify: Firedrills

• 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.

• Pick random files from a backup and restore them.

Verify:

• Use new hardware (servers & disks) to test the viability of your backups before putting the hardware in service

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.

Backup Automation

• Non automated backups are dangerous.• Automation reduces human errors.• Choose your app for backup

– Carbon Copy Cloner– Macrium Reflect– Tar, cpio, dump, dd

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?

Data Compression

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

• Lossy compression is not suitable for many kinds of data. OK for images, video, or sound. Know your data!

• No-loss compression for data base files, applications, etc.

Backup Compression & Encryption

Pros• Compression saves space• Encryption provides security Cons• Lost encryption keys make recovery impossible• Some damaged media can be partially recovered.Consider a Mirror Archive (no compression or

encryption)

Backup Addendum

• Backups slow down service.– Files are write-locked during backup.

• Backups should not be done during peak service hours. Schedule during early AM hours on the weekend.

Restore

• Three 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. (Mirror backup).

• A user wants the restoration to be immediate. The quicker the turnaround, the happier your customer.

Tapes

• Tape is (or was?) 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 tansport• 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 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.

Centralization

• Costs can be reduced through centralization– Tape mounts are labor intensive, so look to

automation. Con– No need for hardware or manpower duplication– Equipment can be interchanged more easily

when centralized.

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.