Modern Distributed Systems Design

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Modern Distributed Systems Design Security and
High Availability

1. Measuring Availability
2. Highly Available Data Management
3. Redundant System Design

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Measuring Availability

• How resiliency and high availability are
  interconnected?
• Define downtime and what causing downtime.
• How to meager availability?

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Measuring Availability
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Define Downtime

• Downtime could be defined by following If a
  user cannot get his job done on time, the system
  is down

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What causing downtime?

• Planned ones that easiest to reduce that
  include scheduled system maintenance,
  hot-swappable hard drives, cluster upgrades and
  even failovers. Usually 30 of all downtime
• People or human factor dumb mistakes and
  complex innovation in IT equipment, software and
  protocols requires greater knowledge of
  engineers. Usually 15 of all downtime
• Software Failures - due to software bugs and
  viruses. (40)

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How to meager availability?

• MTBF
• Availability ---------------------, where
• MTBF MTTR
• MTBF mean time between failures and MTTR -
  maximum time to repair

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What can go wrong?

• Hardware
• Environmental and Physical Failures
• Network Failures
• Database System Failures
• Web Server Failures
• File and Print Server Failures

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The Cost of Downtime.
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Levels of Availability

1. Regular Availability
2. Increased Availability
3. High Availability
4. Disaster recovery
5. Fault-Tolerant System

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Highly Available Data Management

• Data management is the most sensitive area of
  modern distributed systems.
• Quick overview of existing data topologies

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Redundant System Design

• Redundant storage (RAID, Multi-hosting,
  Multi-Pathing, DiskArray, JBOD, etc)
• Failover Configurations and Management
• Introduction to SAN and Fibre Channel protocol
• Security aspects of data management in Storage
  Area Networks

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Redundant storage
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Redundant Storage (RAID 5)
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Failover Configurations and Management

• Failover must meet following requirements
• Transparent to client
• Quick (no more then 5 min, ideally 0-2 min)
• Minimal manual intervention, guaranteed data
  access.

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Failover components

• Two servers, one primary another takeover
• Two network connections, third is highly
  recommended
• All disks on a failover pair should have some
  sort of redundancy
• Application portability
• No single point of failure.

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Symmetric Failover
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Asymmetric Failover
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Fibre Channel, SAN, IP Storage
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Security in IP Storage Networks

• Security in Fibre Channel SANs
• Security Options for IP Storage Networks

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Fibre Channel SAN Security

• Port or hard zoning
• WWN Zoning
• LUN Masking

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Security Options for IP Storage Networks

• iSNS
• LUN Masking as in Fibre Channel and VLAN tagging
• IP Security or IPSec
• ACL