- In this lesson 13.2,
we're gonna focus in on resiliency concepts.
Now, resiliency is the capability to continue operating
even when there's been a disruption
or there's abnormal operating conditions.
I wanna make sure we distinguish resiliency from redundancy.
Redundancy is when we duplicate critical components
or functions with the intention of increasing reliability
and mitigating the risks that are associated
with a single point of failure known as an SPOF.
Now, fault tolerance is a capability
of a system to continue to operate
even in the event of failure
of one or more system components.
Now, categories of resiliency,
are going to include system storage,
power transmission, and site.
So let's go look at all of these.
So for system resiliency itself, right?
Keeping our systems operating
some options we have are load balancing,
clustering, high availability, and fail secure.
So load balancing involves distributing
incoming network traffic
across multiple independent systems
to ensure that no single server
becomes overwhelmed with requests.
Clustering involves grouping multiple systems together
to form a single logical unit or cluster
and we can lose individual components to that cluster
and still be operating.
High availability, you'll see abbreviate is HA,
is the automatic failover capability,
which reduces or eliminates the need to activate
redundant hardware.
Now, there are two approaches, asymmetric and symmetric.
In asymmetric,
we have what's known as an active passive pair
where one device is active and the other device
is powered on but not really doing anything
and it's busy listening for a heartbeat.
Boom, boom, boom, boom, boom, right?
Is that primary device operating?
And if it doesn't hear that heartbeat
at some point it says, okay, I need to come online.
In symmetric, we have an active pair
where both devices are operational, right?
And so one device fails, the other device just continues on.
And then we wanna think about the principle of fail secure
in terms of resiliency.
The idea that a failure will always result
in a secure or trustworthy state.
The rate is redundant, array of inexpensive discs
which is a data storage virtualization technology.
Now, the idea of rate
is that we combine multiple disc drive components
into one or more logical units
for the purpose of fault tolerance and data redundancy
and or performance improvement.
RAID can be configured for mirroring, striping, or both.
The disc mirroring is the process of writing data
on two partitions on separate discs
where just striping is the process of dividing data
into blocks and then spreading those data blocks
across multiple storage devices.
So let's take a look at RAID 1 and RAID 5
which are really the two most common configurations of RAID.
In RAID 1, that's the top graphic you see,
we have two drives, right?
And everything that happens on disc zero
is also gonna happen on disc one.
So you can see on each drive
we have 1A, 1A, 2A2A, 3A3A, 4A4A.
So everything that's happening,
everything that's being written to one
is being written to the other.
That means that we could lose either one of those drives
and continue to be operating.
Now they're both active, right?
It's an active, active pair,
but you know lose either one and we can continue to operate.
So that's dismirroring.
There's still a single point of failure
though with dismirroring,
and that is what if we only have one controller?
So if we have one controller
we still an SPOF, a single point of failure.
And if that controller fails
well we can't access either drive.
So in some configurations
we'll give each drive its own controller.
And when that's true, we'll call it disc duplexing.
We come down to the lower picture rate, level five,
this is gonna be an example of disc striping
and we're doing disc striping with a parody bit.
So disc striping in of itself
stripes the data across multiple drives
but doesn't really give us any resiliency.
But if we do a parody bit across each stripe
then we have the ability to recover a drive if it fails.
So you can see in the first instance we've got 1A, 2A,
3A, and then 4P.
That's a parody bit.
And so what's written right here in that parody bit
is enough information that if we lost the first,
second, or third drive we could reconstruct
the data that was on that pass from that parody bit.
And that parody bit's gonna move around.
So you can see on the next pass we have 1B, 2B, 3P
that's the parody and then 4B.
And on the next one we have 1C, two parody, 3C, 4C.
So our goal in RAID 5
is that we have a performance improvement
because we're striping, but we have the availability, right?
The redundancy, the resiliency, if you will
because we can lose any one of those drives
and we can continue operating
because the data that was on that drive
can be reconstructed from the parody bit.
Next up is power resiliency.
So we can have redundancy having a UPS battery backup,
having a generator, and supplier diversity.
So redundancy just means at the component level
having two or more power supplies or fans
as power supplies are fans, they break, they go, right?
So by making sure that we have multiple of those in a system
we keep operating.
But what if we actually lose our power source?
Well, we can use a UPS uninterruptible power supplies
and that's referred to as a battery backup.
And uninterruptible power supply provides backup power
when the regular power supply fails
or importantly when voltage drops to an unacceptable level.
But the battery is finite, right?
It has at some point the battery will run out.
A generator is a standby secondary limited source
of electrical power when the power grid is down
or inaccessible.
We talked about this way back when we talked
about power and physical security, right?
We said that the important thing about a generator
is we have to make sure that fuel's available
or generator's gonna run on gasoline or on diesel,
need to make sure that the fuel is available to us.
And then supplier diversity
is the idea of having more than one supplier
or access to multiple power grids.
Well, what about our transmission in our wide area networks
or transmission to the internet?
Can we get resiliency in our transmission routing?
And the answer of course is gonna be, yes.
Three options here.
Alternate routing, diverse routing,
and last mile circuit protection.
In alternate routing, we have multiple paths
for our data to travel between two points.
Now, the network can automatically
reroute traffic to an alternate path,
if the primary path becomes unavailable or congested.
In diverse routing, we have data is transmitted
over multiple geographically diverse paths or routes.
So taking different ways to get somewhere.
And there are last mile circuit protection
is where we have redundant last mile circuit
such as multiple fiber optic or copper cables
to provide backup paths for data transmission
in case of failure or outage on one of our primary circuits.
So alternate routing, diverse routing,
and last mile circuit protection.
Well, what if the location
that we work out of isn't accessible
or isn't viable anymore?
Maybe there's been damage to the building of some kind
or just maybe there's a been a natural disaster
and we can't get to the building.
So let's talk about alternate physical sites
physical sites or sites that are managed,
maintained and monitored, you know, by the organization.
So some options we have for sites
and this can be sites where our users are working.
It could be sites where we're moving our data center to
but these are alternate locations.
AOC site is a site that just has basic HVAC
infrastructure that stands for heating,
ventilation and air conditioning.
So it's just a space, right?
It has basic HVAC, but it's really just an empty shell.
There's no server related or communications equipment.
So if I have to move there, I need everything.
I need all my equipment,
I need my cabling, I need desks, I need computers,
I need pencils, I need paper, I need everything.
A warm site is a site that does have HVAC,
heating ventilation, air conditioning,
and we've set it up a bit.
It has servers and it has communication infrastructure
and equipment.
Now, the systems probably will need to be configured,
updated they might need to be patched,
they might need new antivirus
and data will need to be restored.
In a hot site,
well, that's gonna have HVAC, it'll have servers,
it'll have our communications infrastructure
and it'll have equipment,
and it's fully configured and ready to operate.
So we keep those systems up to date, right?
We're patching them if we're making sure that
you know, our antivirus is up to date.
If there's anything that we've changed
in our configuration management
we're updating the systems as well.
So the systems are fully configured and ready to go.
And data's been replicated.
So either we've had asynchronous or synchronous replication
so we should be back in business pretty quick.
And lastly is a mirrored site.
And a mirrored site isn't identical
or nearly identical site that's already operational, right?
It's operational in concert with the primary site
on a load balancing basis.
So we lose one site, we're still operational
at the other site.
Then we have a couple of options
for alternate third party sites, a mobile site,
a reciprocal site, and a cloud-based site.
A mobile site is going to be a transportable module unit
that will show up at your doorstep, right?
And it has your pre-ordered hardware and software
and you've probably been sending your backups
to whoever owns that mobile site.
That sounds great, except there's a lot of situations
where it's really not gonna work
because the delivery site must provide access roads,
water, waste disposal, power and connectivity.
So particularly in a natural disaster,
it might not be your best choice.
A reciprocal site is based on an agreement
to have access to or use another organization's facilities.
That's a little scary.
But you know, often used by very small companies
but you know, you don't necessarily know
what they're gonna have available to you.
You may not be confident
in their privacy or security controls.
You know, their physical controls,
their environmental controls, and just the idea that,
okay, if I go down, I'm gonna use somebody else's facility.
That seems to me to make much more sense,
if it's just I need office space and desk space
opposed to I'm gonna put my servers in this new location.
And lastly, we have DRAAS,
which is disaster recovery as a service.
Now cloud-based disaster recovery as a service
offers full recovery in a cloud-based environment.
So lots of options for resiliency, right?
Site, in power, in system, in data, right?
And we always have to keep in mind that systems fail
and problems occur
and we have to be ready to continue to operate.
And that's really the goal of resiliency
to be able to continue to operate
in abnormal operating conditions.
That my friends, brings us to a three second challenge.
Five challenge questions, three seconds each.
No question.
You know how to do it.
Question one, the capability to continue to operate
in abnormal conditions.
One, two, three, that's gonna be resiliency.
Number two, this technology commonly used
for fault tolerance.
Showed you two versions One, two, three.
And that's gonna be RAID.
Number three, when data is transmitted
over multiple geographically diverse paths or routes
One, two, three, it's gonna be diverse routing.
Number four, this site has HVAC
servers and communications infrastructure and equipment.
Systems might need to be configured.
Data needs to be restored. One, two, three,
That's it gonna be, it's a warm site.
And lastly, number five, the process
of writing data on two partitions on separate discs.
One, two, three.
And that's known as disc mirroring.
And if we add another controller,
it would be disc duplexing.
Okay, let's do a security in action.
This one is about uptime, 99.999%.
Your organization is negotiating a contract
with a new client.
They're requiring the service that you're proposing
to have an uptime of 99.999%.
Now, before agreeing to these terms,
you recommend an internal discussion
to evaluate our current capacity
and to determine the investment required
to guarantee this level of availability.
Now, the standard configuration what you have right now
is RAID 5 with the ability to hot swap drives.
So if a drive fails
you can pull one out and put the other in.
But is that enough?
Is that gonna get you to 99.999
plus are there other things you need?
So my question to you
is what discussion topics would you raise?
So a quick recap,
you are negotiating a contract with a new client.
They're saying, "I want you to be up 99.999% of the time."
And you're saying, "Okay, well, but before we do that
we really need to evaluate our current capacity
and see what kind of investment would be required
to guarantee this level of availability."
Maybe this contract is not worth it.
What do you do right now?
Well, your current configuration is RAID 5.
That's gonna be disc striping with parody
with the ability to hot swap a drive.
Hot swap means you can just take a drive out on the fly
and put a new one in.
So what topics are you gonna raise?
Go ahead and put me on pause,
write down those discussion topics, then come on back.
Well, 99.999% of time,
and you see that in marketing all the time,
implies no more than 5.26 minutes
of unavailability per year.
That's a really tough nut to achieve.
Now, RAID is a disk-space fault tolerance strategy.
Pretty good strategy, right?
Especially with our hot swap drives.
But it doesn't extend to any other components, right?
It's only about drives.
So investments in high availability systems
are gonna need to be made
either asymmetric, high availability or symmetric.
Remember, we can either have an active passive pair
or an active active pair.
The consideration should also be given to site resiliency.
What happens if there's a problem at your site?
And then additional downtime considerations include,
necessary maintenance windows for upgrades
and for patch management.
So trying to achieve 5.26 minutes
of unavailability per year really is a very high bar.
So before you're agreeing to that contract,
right you really wanna go through
what are all the things that you need
how is it different than what you have?
So a gap analysis
and what type of investment is gonna be required.
And then ultimately doing a cost benefit analysis
doing all that.
That's definitely security and action.
It's a pretty big word cloud.
Once again, take your time,
make sure that you understand all of these concepts
and terms.
You can speak to them confidently.
And when you're ready, come on over to the next lesson.
I'll be waiting for you right there.