WEBVTT 00:00:00.940 --> 00:00:07.730 Design resilience involving availability classes is our next focus. From ISO 00:00:07.730 --> 00:00:13.170 22237 documentation, we have what are called availability classes, and they 00:00:13.170 --> 00:00:17.690 number four. They are connected to power distribution and have the ability to 00:00:17.690 --> 00:00:19.730 maintain resilience during disruption. 00:00:19.740 --> 00:00:25.030 Class 1 signifies a single path that has no resilience or 00:00:25.040 --> 00:00:28.400 no redundancy, so when planned maintenance or unplanned 00:00:28.410 --> 00:00:33.010 outages cause service outage, it's dependent on that single system. 00:00:33.340 --> 00:00:37.070 In a Class 2 single‑path resilience, 00:00:37.080 --> 00:00:41.610 you have components within devices that are resilient. 00:00:41.720 --> 00:00:45.790 We'll see that in just a moment illustrated by means of a switch. 00:00:45.800 --> 00:00:51.140 In Class 3, you have multipath resilience, and this is provided by redundant 00:00:51.140 --> 00:00:54.960 systems, so then you have concurrent capability to repair, 00:00:54.970 --> 00:00:59.570 operate, and to solution based off of separate controls and separate 00:00:59.570 --> 00:01:04.379 paths. In a Class 4, Now you have a multipath fault tolerant, where 00:01:04.379 --> 00:01:10.580 your redundant systems are actually active in the processing. So Class 00:01:10.580 --> 00:01:15.140 3 could be viewed as active/passive, whereas Class 4 would be 00:01:15.150 --> 00:01:20.630 active/active. If you were to look at Uptime Institute's view of what 00:01:20.640 --> 00:01:25.100 the data center looks like, the data center site infrastructure 00:01:25.100 --> 00:01:26.950 standards are in tiers. 00:01:26.960 --> 00:01:31.160 They have an unbiased international advisory organization that provides 00:01:31.160 --> 00:01:36.100 the baseline that many enterprises use to rate their data centers. In a 00:01:36.100 --> 00:01:39.850 Tier I classification, you have no redundancy, 00:01:39.940 --> 00:01:46.810 but there is a requirement for dedicated uninterruptible power supplies and 12 00:01:46.820 --> 00:01:51.840 hours of on‑site fuel storage. In a Tier II environment, 00:01:51.850 --> 00:01:55.940 you have the capacity components that are redundant within a 00:01:55.940 --> 00:01:59.710 system, but you don't have redundant systems. In a Tier III, 00:01:59.710 --> 00:02:01.380 you have redundant systems, 00:02:01.390 --> 00:02:05.410 one of which is active and the other one is passive. And in Tier IV, 00:02:05.410 --> 00:02:11.150 you have an active/active environment for systems. These make a 00:02:11.150 --> 00:02:17.550 direct parallel to what was described in the Class systems of ISO 00:02:17.550 --> 00:02:22.870 22237, but let's see what does this look like if we were to actually 00:02:22.870 --> 00:02:24.160 visualize a system. 00:02:24.540 --> 00:02:29.670 So, in this example, we have a data switch. In a Tier I 00:02:29.670 --> 00:02:31.960 environment, you have no redundancy. 00:02:31.970 --> 00:02:36.350 So let's say that this switch then had a management interface labeled 00:02:36.360 --> 00:02:40.460 Interface 1 and a power supply labeled Power Supply 1. 00:02:40.540 --> 00:02:44.470 If there were failures in the interface or failures with the power supply, 00:02:44.480 --> 00:02:50.930 that's it, there's nothing left. In a Tier II environment, now it's still a 00:02:50.930 --> 00:02:55.310 single switch, but you have redundant capacity components. 00:02:55.320 --> 00:03:01.930 See the picture? Tier III, now we duplicate the redundant switch and we 00:03:01.940 --> 00:03:07.080 actually make it so that one switch is processing actively and the other 00:03:07.080 --> 00:03:13.350 switch is not processing actively. In a Tier IV environment, we move from 00:03:13.360 --> 00:03:18.270 active/passive to an active/active environment, where we're actually 00:03:18.270 --> 00:03:20.300 processing with both of them. 00:03:20.310 --> 00:03:25.030 Now, while you may get performance gain, that is not the purpose. 00:03:25.070 --> 00:03:29.250 Remember, our focus is on availability classes.