Tech TopX: Protection Domain
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Tech TopX: Protection Domain


Hi! Welcome to another edition of Tech
TopX. My name is Al Harper and I’m an SRE here in RTP in North Carolina, and
today we’re going to be talking about protection domains and how you can use
them to back up information on your cluster. As we go through the demo, we’ll
be showing you various terms so keep an eye out for those. Our demo today will
use NOS version 4.0.2.1, though any of the information we talk about is
applicable to any of the NOS 4.x versions. If you’re using 3.5.x, please
note that the information should still be applicable, it just may look a little
different for you. Alright, let’s jump right into the demo. So let’s take a look
at protection domains in Prism. We’ll navigate from the home page in Prism to
data protection and then from here we’ll see our Protection Domains listed in the
table. When we click on PD-1, that’s the name of our Protection Domain in this
demo. We can see the details down in the bottom left, including the name, the mode,
it’s active meaning that VMs are currently powered on, and the next
snapshot time and the number of VMs. When we click over here on the right, we can
see how many VMs are listed and what they are, we can unprotect them, and
note that if you unprotect a VM from a Protection Domain, it doesn’t delete the
VM; all it does is tells it in the future not to back up any more VMs. This will
also leave the snapshots there for that VM. So it’s not going to delete anything
it just takes care of things going forward. When we click on schedules we
can see the schedules associated with it, as well as, the retention policy for each
schedule. Local snapshots will show our time stream with our most recent
snapshot listed here at the top. Remote snapshots, we won’t really use
here; neither when we use metrics, since those are associated with remote site
alerts are going to be any alerts that are specific to protection domains and
the events is just an event log for everything that you’ve done and a
timestamp associated with it. So let’s go through and create a new protection
domain to see what that looks like. We click on the + Protection Domain at
the top and then we can name it. We’ll name it ‘pd2’ and then we can add virtual
machines to it. From here, we’ll just check the box for the VM that we’d like
to add to the protection domain. We’re going
to leave it in consistency group named after the VM, since that’s not important
to us. An application consistent snapshot will invoke VSS to get us a snapshot
with the RAM dumped out to it, we don’t need that, so we’re not going to check it.
We click protect which adds it over here as a protected VM and now we can click
Next. From here we can create a schedule for
it, you can set it up as minutely, hourly, daily, weekly, or monthly. Select a
start time and an end time, we’re gonna have it start right now and we will just
have it continue indefinitely. Let’s set it up to repeat every one hour and keep
three snapshots. It’s important to remember how the retention policy
affects the schedule so all this means is that we have VMs backed up every hour and we’re holding onto three of them meaning that
they will have an expiry time of three hours from the time that they are
created. This doesn’t mean that we’re going to delete snapshots when they’re
done, it simply means that after three hours when we come on to that next one,
the oldest one will be marked for expiration, Curator will be the one to go
in and remove that at a later time. So let’s create the schedule and then close
out of this. We can see that pd-2 was created and it looks like what we would
expect to see down here and if we look at local snapshots, we have one created
instantly right now. You’ll notice we also have a restore button here. If you
want to rollback your VM you can do that through this process. You can choose the
VM that you want to restore. We have two options here. We can restore the VM, which
will erase what’s currently there and rewrite it with the snapshot. So any
information that was there at the time this will put this in place. We also have
the clone option. When we click clone, it’s going to leave the VM win7-1
there and it will create an additional VM based off the snapshot that we’re
referencing. It’s important here you do need to create a file path, so you would
actually have a slash and then whatever you wanted to call it. So if we did win7-1-clone and click OK, it will go ahead and create that restoration for us
and clone it. So now that we have that protection domain created,
let’s look really quickly at the retention policy for the schedule
and something that we have called the minimum snapshot count. The minimum
snapshot count is a hidden value that we don’t show and by default it is set to
5, what this means is that for this protection domain, we have this set up to
back up every one hour and hold on to 3, which we can see that if we look
here the create time is 12:56 and the expiration time is 3:56. So that’s 3 hours from now that that will be set to expire. As long as
everything continues, we should build up a snapshot every hour and so that
expiration time is normal. However, outside of Prism it is going to hold on
to 5 snapshots by default, just to make sure that everything’s okay. That’s
just set up as a safety net. If you have a cluster that has any sort of space
concerns and you’re backing up large VMs, it’s a good idea to go through and set
your minimum snapshot value to be the same as your schedule. That way you don’t
have unnecessary snapshots taking up space. So, we’re gonna be looking at this
in ncli in the NOS 4.0.2.1 code versions. So let’s pop over to ncli. We
already have a session connected here logged into one of our CVMs. Select
connect to ncli. We’re gonna flag – h to true and this will actually show hidden
commands for us. So now that we’re connected, we can run the command ‘pd set-min-snapshots’ and then we want to say the name and this would be the name of
the protection domain, so we’ll do pd2, and then we set the minimum snapshot
value. The minimum snapshot value by default is 5, so we’re gonna set this
to 3, so that it lines up with the retention policy that we have set up in
Prism. We run this we get the following output, ‘minimum snapshot for protection
domain pd2 updated successfully’. There’s not a way to view what the minimum
snapshot value is currently set to, but it’s always safe to go up in here and
set it yourself. Note that if we did set the minimum
snapshots to 2, since the retention policy is 3 and that’s a greater
value, it will hold on to 3. So this is just there as a safety net, but it’s
always something to keep in mind. Alright guys, thanks for tuning in.
Everything that I’ve talked about here can be located in the product
documentation guides which are on portal.nutanix.com and everything with
protection domains is specifically in the web console guide. Be sure to
check back for more Tech TopX.

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