RTO & RPO
- RTO of 2 hours indicates that organization needs to ensure that their system downtime should not exceed 2 hours.
- RPO of 2 hours indicates that organization needs to ensure that their data loss should not exceed 2 hours of data captured.
- In any given scenario, for critical systems, RTO is zero or near zero. Similarly, for critical data, RPO is zero or near zero.
- lower the RTO/RPO, higher the cost of maintenance of environment.
- low RTO/RPO indicates that disaster tolerance is low. Other way round, if disaster tolerance is low, RTO/RPO should be low.
- when RTO is low, mirrored site or hot site is recommended.
- when RPO is low, mirror imaging or real time replication for data back-up is recommended.
- where RPO is zero, synchronous data backup strategy to be used.
- Both RTO & RPO are based on time parameters. The lower the time requirements, the higher the cost of recovery strategies.
- RTO (Acceptable System Downtime)
- RPO (Acceptable Data Loss)
Alternate Recovery Site
- Mirrored site is fastest mode of recovery and then hot site.
- Cold site is slowest mode of recovery.
- For critical system, mirrored/hot sites are appropriate option.
- For non-critical system, cold site is appropriate option.
- Reciprocal agreement will have lowest expenditure in terms of recovery arrangement.
# Mirrored Site
Already Available - Space & Basic Infra, All IT equipment, Updated database
Required - hardly anything
# Hot Site
Already Available - Space & Basic Infra, All IT equipment
Required - -Updated database
# Warm Site
Already Available - Space & Basic Infra, Some IT equipment
Required - Needed IT equipment, Updated database
# Cold Site
Already Available - Space & Basic Infra
Required - Needed equipment, Updated database
# Mobile Site
- Mobile sites are processing facilities mounted on a transportable vehicle and kept ready to be delivered.
- A mobile site is a vehicle ready with all necessary computer equipment, and it can be moved to any cold or warm site depending upon the need. The need for a mobile site depends upon the scale of operations.
# Reciprocal Agreement
- Reciprocal agreements are the agreements wherein two organizations (mostly having similar processing) agree to help each other in case of emergency. Reciprocal agreements are the least expensive because they usually rely on agreement between two firms. However, they are the least reliable.
Physical Network Media:
- Fiber-optic cables have proven to be more secure than the other media. They have very low transmission loss, not affected by EMI and preferred choice for high volumes and long distance calls.
# Attenuation:
- Weakening of signals during transmission.
- Exists in both wired and wireless transmissions.
- Length of wire impacts the severity of attenuation.
# Electromagnetic Interference (EMI):
- EMI is a disturbance generated by an external source that affects an electrical circuit.
- The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.
- EMI is caused by electrical storms or noisy electrical equipments (e.g. motors, fluorescent lighting, radio transmitters etc.)
# Cross-Talks:
- Crosstalk is electromagnetic interference from one unshielded twisted pair to another twisted pair, normally running in parallel.
- Only occurs in wired communication
# Sags, Spikes, and surges:
- Only occurs in wired communication
# Multipath Interference:
- Only occurs in wireless communication
- Using separate conduits for data cables and electrical cables, minimizes the risk of data corruption due to an induced magnetic field created by electrical current.
# Alternate Routing:
- Method of routing information via an alternative medium, such as copper cable or fiber optics.
Last mile circuit protection:
Last mile circuit protection provides redundancy for local communication loop.
Long haul network diversity:
Long haul network diversity provides redundancy for long distance availability.
# Diverse Routing:
- Diverse routing is the method of routing traffic through split-cable facilities or duplicate-cable facilities.
- In alternate routing alternate type of cables are used such as fiber optics or copper cable
- In diverse routing same type of cable is used either in duplicate or by splitting.
Gateway - Application Layer (7th Layer)
Switch stores MAC address in a look up table
# Bridges:
Act as store-and-forward devices in moving frames toward their destination. This is achieved by analyzing the MAC header of a data packet. By examining the MAC address, the bridge can make decisions to direct the packet to its destination. It has the capacity to store frames and act as a storage and forward device.
# Backup schemes:
Full Backup - Every time data backup is taken of full database irrespective of earlier backup.
Incremental Backup - Backup is taken only of data changed since last backup (last backup can be either full backup or incremental backup).
Differential Backup - Backup is taken only of data changed since last full backup (last back to be full back-up only).
# Differential Backup
Full backup taken at Monday
- On Tuesday backup taken for changes made after Monday’s backup
- On Wednesday backup taken for changes made after Monday’s backup (ignoring Tuesday’s backup)
- On Thursday backup taken for changes made after Monday’s backup (ignoring Tuesday’s & Wednesday’s backup)
- On Friday backup taken for changes made after Monday’s backup (ignoring Tuesday’s , Wednesday’s & Thursday’s backup)
# Incremental Backup
Full backup taken at Monday
- On Tuesday backup taken for changes made after Monday’s backup
- On Wednesday backup taken for changes made after Tuesday’s backup
- On Thursday backup taken for changes made after Wednesday’s Backup
- On Friday backup taken for changes made after Thursday’s Backup
# Storage Capacity for each backup Scheme:
-Full Backup- Requires more time and storage capacity as compared to other two schemes.
-Differential- Requires less time and storage capacity as compared to full backup but more time and storage capacity as compared to Incremental.
-Incremental- Requires less time and storage capacity as compared to other two schemes.
# Restoration Capability for each backup Scheme:
-Full Backup- Fastest of all three schemes.
-Differential- Slower than Full backup but faster than incremental.
-Incremental-Slowest of all three schemes.
- RTO of 2 hours indicates that organization needs to ensure that their system downtime should not exceed 2 hours.
- RPO of 2 hours indicates that organization needs to ensure that their data loss should not exceed 2 hours of data captured.
- In any given scenario, for critical systems, RTO is zero or near zero. Similarly, for critical data, RPO is zero or near zero.
- lower the RTO/RPO, higher the cost of maintenance of environment.
- low RTO/RPO indicates that disaster tolerance is low. Other way round, if disaster tolerance is low, RTO/RPO should be low.
- when RTO is low, mirrored site or hot site is recommended.
- when RPO is low, mirror imaging or real time replication for data back-up is recommended.
- where RPO is zero, synchronous data backup strategy to be used.
- Both RTO & RPO are based on time parameters. The lower the time requirements, the higher the cost of recovery strategies.
- RTO (Acceptable System Downtime)
- RPO (Acceptable Data Loss)
Alternate Recovery Site
- Mirrored site is fastest mode of recovery and then hot site.
- Cold site is slowest mode of recovery.
- For critical system, mirrored/hot sites are appropriate option.
- For non-critical system, cold site is appropriate option.
- Reciprocal agreement will have lowest expenditure in terms of recovery arrangement.
# Mirrored Site
Already Available - Space & Basic Infra, All IT equipment, Updated database
Required - hardly anything
# Hot Site
Already Available - Space & Basic Infra, All IT equipment
Required - -Updated database
# Warm Site
Already Available - Space & Basic Infra, Some IT equipment
Required - Needed IT equipment, Updated database
# Cold Site
Already Available - Space & Basic Infra
Required - Needed equipment, Updated database
# Mobile Site
- Mobile sites are processing facilities mounted on a transportable vehicle and kept ready to be delivered.
- A mobile site is a vehicle ready with all necessary computer equipment, and it can be moved to any cold or warm site depending upon the need. The need for a mobile site depends upon the scale of operations.
# Reciprocal Agreement
- Reciprocal agreements are the agreements wherein two organizations (mostly having similar processing) agree to help each other in case of emergency. Reciprocal agreements are the least expensive because they usually rely on agreement between two firms. However, they are the least reliable.
Physical Network Media:
- Fiber-optic cables have proven to be more secure than the other media. They have very low transmission loss, not affected by EMI and preferred choice for high volumes and long distance calls.
# Attenuation:
- Weakening of signals during transmission.
- Exists in both wired and wireless transmissions.
- Length of wire impacts the severity of attenuation.
# Electromagnetic Interference (EMI):
- EMI is a disturbance generated by an external source that affects an electrical circuit.
- The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.
- EMI is caused by electrical storms or noisy electrical equipments (e.g. motors, fluorescent lighting, radio transmitters etc.)
# Cross-Talks:
- Crosstalk is electromagnetic interference from one unshielded twisted pair to another twisted pair, normally running in parallel.
- Only occurs in wired communication
# Sags, Spikes, and surges:
- Only occurs in wired communication
# Multipath Interference:
- Only occurs in wireless communication
- Using separate conduits for data cables and electrical cables, minimizes the risk of data corruption due to an induced magnetic field created by electrical current.
# Alternate Routing:
- Method of routing information via an alternative medium, such as copper cable or fiber optics.
Last mile circuit protection:
Last mile circuit protection provides redundancy for local communication loop.
Long haul network diversity:
Long haul network diversity provides redundancy for long distance availability.
# Diverse Routing:
- Diverse routing is the method of routing traffic through split-cable facilities or duplicate-cable facilities.
- In alternate routing alternate type of cables are used such as fiber optics or copper cable
- In diverse routing same type of cable is used either in duplicate or by splitting.
Gateway - Application Layer (7th Layer)
Switch stores MAC address in a look up table
# Bridges:
Act as store-and-forward devices in moving frames toward their destination. This is achieved by analyzing the MAC header of a data packet. By examining the MAC address, the bridge can make decisions to direct the packet to its destination. It has the capacity to store frames and act as a storage and forward device.
# Backup schemes:
Full Backup - Every time data backup is taken of full database irrespective of earlier backup.
Incremental Backup - Backup is taken only of data changed since last backup (last backup can be either full backup or incremental backup).
Differential Backup - Backup is taken only of data changed since last full backup (last back to be full back-up only).
# Differential Backup
Full backup taken at Monday
- On Tuesday backup taken for changes made after Monday’s backup
- On Wednesday backup taken for changes made after Monday’s backup (ignoring Tuesday’s backup)
- On Thursday backup taken for changes made after Monday’s backup (ignoring Tuesday’s & Wednesday’s backup)
- On Friday backup taken for changes made after Monday’s backup (ignoring Tuesday’s , Wednesday’s & Thursday’s backup)
# Incremental Backup
Full backup taken at Monday
- On Tuesday backup taken for changes made after Monday’s backup
- On Wednesday backup taken for changes made after Tuesday’s backup
- On Thursday backup taken for changes made after Wednesday’s Backup
- On Friday backup taken for changes made after Thursday’s Backup
# Storage Capacity for each backup Scheme:
-Full Backup- Requires more time and storage capacity as compared to other two schemes.
-Differential- Requires less time and storage capacity as compared to full backup but more time and storage capacity as compared to Incremental.
-Incremental- Requires less time and storage capacity as compared to other two schemes.
# Restoration Capability for each backup Scheme:
-Full Backup- Fastest of all three schemes.
-Differential- Slower than Full backup but faster than incremental.
-Incremental-Slowest of all three schemes.
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