Calculating Applications Service Level Agreements

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Time
3 hours 51 minutes
Difficulty
Beginner
CEU/CPE
4
Video Transcription
00:00
Let's talk about how azure SLA's can impact your application.
00:05
Any system can experience a failure.
00:08
Hardware breaks networking, has transient failures, and software has bugs and crashes,
00:14
even with all the redundancy built into azure services. And sometimes whole regions can experience a disruption
00:21
amongst the many things you need to think about when designing your applications is also its reliability.
00:28
Knowing your application requirements, you can make more informed decisions as to what as your services to use to achieve your performance goals
00:38
using as your zealous in your application architecture, you can build your own application SLA's that you can provide your customers with
00:47
resiliency is the ability of a system to recover from failure.
00:51
The goal is not to avoid failures, but to be able to respond to failures and avoid downtime or data loss.
00:58
Important components of resiliency are high availability and disaster recovery.
01:03
When designing your application, you should always design for resiliency.
01:08
One of the common traps application designers fall into is to maximize availability by implementing measures to prevent application failures.
01:18
The problem with this is that implementing preventative measures can be difficult and expensive.
01:23
Preventative measures also complicate the systems
01:26
increased availability always results in increased complexity, which results in higher cost.
01:34
Knowing the availability requirements for your application will determine how you handle the additional complexity.
01:42
One thing to consider when designing your application. SLA's is the level of automation built into your application.
01:49
If your application requires manual intervention and has no built in self healing capabilities,
01:55
achieving high SLA's is going to be difficult.
01:59
L. A. Is higher than three. Nines are hard to achieve.
02:02
You need to make sure that the effort warrants the return on investment,
02:07
the smaller the time window for your performance targets. The lower is to the tolerance you need to consider.
02:14
Do not use hourly or daily up times in your SLs because a small failure can throw you off of your metrics.
02:23
Here's how you can approach the calculation of your application. SLA's
02:29
Let's assume that you have a single VM that stores data into Cosmos DB
02:34
The S L. A. For the VM is 99.9% while the S L. A. For the Cosmos DB is 59
02:40
The composite s L A. For that system is 99.9% times 99.999 or 99.899 and something which is lower than the S L A. For both participating services.
02:55
This is understandable.
02:59
If this is not satisfactory for your application, you can, of course, improve it by adding a secondary VM.
03:07
The probability of simultaneous failure of both VMS is 0.1 times 0.1 or 0.1%.
03:20
The L A for simultaneously running VMS is 69 while the combined for the system is 99.9989%.
03:30
This is much closer to the for the most reliable component of the system.
03:35
Cosmos TV,
03:36
however,
03:37
notice that the complexity and the cost of the system has increased with the addition of another VM that will require maintenance and incur additional costs.
03:47
Now you are aware how azure SLS can impact your application SLS and how you can combine services to improve them.
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