Backing up the virtual datacentre

Charles Llewellyn and Matt Johnson

Eduserv in 3 slides

• Founded in 1999• Part of the community since 1988• SME (150 staff, £12m turnover)• Not for profit & registered charity

What we do…

• Infrastructure services• Cloud services• Managed services• Consultancy• Web development• Licence negotiation• Identity & access management

Who we work with…

Agenda

• Understanding your data• Defining backup requirements• Overview of Eduserv’s data and requirements• Problems with traditional backups in a virtual

datacentre• Solutions to traditional backup issues

Terminology

• Recovery Point objective• Oldest point the data stored on backups can be

• Recovery Time Objective• Time allowed to restore the data

• Backup window• Time which the backup window must complete in

Terminology

• Backup/Archive/DR• Backup: used to recover data following loss/corruption• Achieve: used to store data long term• Disaster recovery: policy and process to provide service

continuation in event of catastrophic failure

Terminology

• Consistency• Crash consistent: does not provide guarantees of data

integrity• File system consistency: guarantees file system state• Application consistency: guarantees application

consistency

Understand your data

• Data structure• Highly transactional/static content

Highly transactional application

Backup server

Transactional data

Backup server

Static application

Static data

Understand your data

• Data structure• Highly transactional/static content• Large or small files

File Metadata

Backup server

File Data

File Metadata

File Data

File Metadata

File Data

Small files

File Metadata

Backup server

File Data

Large files

Understand your data

• Data structure• Highly transactional/static content• Large or small files• Rate of duplication

• Data use• Useful life of the data• Does the data need to be backed • Who controls the data

Requirements

• Why is the data backed up• Recovery Time Objective• Recovery Point Objective• Retention period• Offsite requirements• Cost

Virtual server data

• Large and small files• High percentage of duplicated data• Data change rate varies• Typically short data life• What we don’t backup• We don’t control the data

Virtual server backup requirements

• Restores: recover from deletion/corruption• Backup service that is independent from the OS • Fast backup and restores with low overhead• Short retention period• Ability to restore entire VMs or individual files• Single site/dual site• Self service backups• Scalability• Low cost

A very…brief backup history

• One to one relationship between servers and backup disks

http://www.flickr.com/photos/sylvar/31436967/sizes/l/in/photostream/

A very…brief backup history

• Central backup tape repository for backup storage• Accessed via a client side agent

• Traditional approach was used initially for virtual machine backups

Problems with traditional backups in a virtual world

• Processing• High consolidation ratios mean higher impact• Agent based backups require client resources

• Streaming to tape• No parallelisation• High latency• Issues with long term incremental backups• High administrative overhead

Problems with traditional backups in a virtual world

• Restore time• Slow to locate and load tapes, and to locate data on tape• Slow to restore entire VM as process is the same as

physical server• Storage footprint• Large storage foot print required as de-dup etc. cannot

easily be used• To improve restore time full backups taken weekly

Resolutions to issues – disk to disk

• Enhanced parallelisation of jobs• Reduced administrative overhead• Improved restore time• Reduced foot print

Resolution – move backups to the hypervisor

• No more agents :-)• Change block tracking

Change Block Tracking

Resolution – move backups to the hypervisor

• No more agents :-)• Change block tracking• Single backup to provide file level and image level

restore

Virtual machine file make-up

Resolution – move backups to the hypervisor

• No more agents :-)• Change block tracking• Single backup to provide file level and image level

restore• Forever/Reversed incremental

Forever incremental

Reversed incremental

Resolution – move backups to the hypervisor

• No more agents :-)• Change block tracking• Single backup to provide file level and image level

restore• Forever/Reversed incremental• Scale-out infrastructure

Overview of backup infrastructure

What does this mean?

• 170GB machine with static data• Traditional backup: ~3 hours• Virtualised backup: ~2 minutes

• ~230TB VM data• Virtualised backup: ~3 hour backup window

• Continue meeting the backup window with horizontal scaling

Conclusion

• Understand your data• Understand your requirements• For virtual backups• Look at disk to disk for virtual platforms• Make sure you take advantage of low processing

overhead such as change block tracking and single backups for image and file level restores

• Only backup what you need to!

Thank you – questions?

Charles Llewellyn and Matt Johnson