AZ-900 Certification Notes

Chapter 6.5 - Storage Redundancy

Accidents Happen! These could be in the form of Hardware Failure such as a corrupted disk. Or accidents can have a wider scope in which an entire location (Zone/Regional Outage) is temporarily unavailable. For these scenarios, the concept of data redundancy can protect against these unplanned accidents/failures.

Importance of Data Redundancy

Redundancy: Multiple, Replicated Copies of Data

If one copy fails/is inaccessible, data is still available. Azure Storage always creates multiple copies of your data:

• Automatic
• Minimum of three copies
• Invisible to end user

Multiple Redundancy Options

• Different location scopes
  • Single zone
  • Multiple zones
  • Multiple regions
• Higher availability = higher cost

Redundancy Options at a Glance

• Single Region
  • Locally Redundant Storage (LRS)
  • Zone-Redundant Storage (ZRS)
• Multi-Region
  • Geo-Redundant Storage (GRS)
  • Geo-Zone-Redundant Storage (GZRS)

All options include:

• Three copies in primary region
• Three copies in secondary region (multi-region options)

Locally Redundant Storage (LRS)

Three copies in a single location (datacenter/zone)

• Lowest-cost option
• Protect against single disk failure
• Does not protect against zone or regional outage

Zone-Redundant Storage (ZRS)

Three copies across three availability zones

• One copy in each zone
• Protect against zone outage, but not regional outage

Geo-Redundant Storage (GRS)

Three copies in two different regions

• Three copies in primary regional physical location (LRS)
• Three copies in secondary (paired) region physical location (LRS)
• Protect against primary region failure, but no primary region zone redundancy
• Can configure read access from secondary region for high availability
  • In the event of a primary region failure, the failover process of accessing your data from the secondary region will be relatively much quicker than if we had this option disabled

Geo-Zone-Redundant Storage (GZRS)

Maximum redundancy!

• Copy across three availability zones in primary region (ZRS)
• Three copies in secondary region physical location/zone (LRS)
• Protect against primary region failure AND primary region zone failure
• Can also configure read access from secondary region for high availability

Summing It Up

Azure Storage automatically replicates data for redundancy

• Three copies in single region
• Six copies across two paired regions
  • Three in each region Redundancy options vary by availability and cost
• Single zone
• Multiple zones in a single region
• Across regions
  • Single/multi-zone in primary region