WEBVTT 00:00.930 --> 00:01.763 Instructor: In the last section, 00:01.763 --> 00:04.560 we spoke about what a volume is in the role of Kubernetes. 00:04.560 --> 00:05.940 We're now going to start to talk about 00:05.940 --> 00:08.580 these two other types of objects that we can create as well, 00:08.580 --> 00:12.030 a persistent volume claim and a persistent volume. 00:12.030 --> 00:14.460 We'll first begin by comparing and contrasting 00:14.460 --> 00:17.640 the differences between a persistent volume and a volume. 00:17.640 --> 00:19.560 So quick diagram to figure out what 00:19.560 --> 00:22.380 the difference is between these two are. 00:22.380 --> 00:23.730 All right, so in this diagram. 00:23.730 --> 00:24.630 on the left hand side, 00:24.630 --> 00:26.970 we have a Postgres deployment with a volume. 00:26.970 --> 00:28.170 That's exactly what we were talking 00:28.170 --> 00:29.550 about in the last section. 00:29.550 --> 00:30.630 We had said that a volume 00:30.630 --> 00:34.738 is going to be some long term storage that is tied to a pod. 00:34.738 --> 00:38.070 Whenever the pod is created, the volume is created. 00:38.070 --> 00:40.470 If a container crashes for any reason, 00:40.470 --> 00:42.240 the volume will stick around. 00:42.240 --> 00:43.680 The volume will persist. 00:43.680 --> 00:44.670 And so we had said that 00:44.670 --> 00:47.280 if we end up with a new Postgres container, 00:47.280 --> 00:48.390 for whatever reason, 00:48.390 --> 00:50.520 no problem, it can freely connect back 00:50.520 --> 00:54.390 to this existing volume that had been created. 00:54.390 --> 00:56.430 And so we can kind of imagine that the old container 00:56.430 --> 00:58.710 might fall away and it gets replaced with this new one. 00:58.710 --> 01:01.590 Still gets access to all that volume data. 01:01.590 --> 01:04.500 However, if the entire pod crashes for any reason, 01:04.500 --> 01:08.400 everything inside the pod is lost, including that volume. 01:08.400 --> 01:09.840 All right, so that's a volume. 01:09.840 --> 01:11.520 That's what we spoke about in the last section. 01:11.520 --> 01:13.470 So now let's compare and contrast that 01:13.470 --> 01:15.780 against a persistent volume. 01:15.780 --> 01:17.070 With a persistent volume, 01:17.070 --> 01:20.265 we are creating some type of long term durable storage 01:20.265 --> 01:23.430 that is not tied to any specific pod 01:23.430 --> 01:26.700 or any specific container. So you can kind of imagine 01:26.700 --> 01:28.890 that the persistent volume is outside the pod, 01:28.890 --> 01:31.170 completely separate from the pod. 01:31.170 --> 01:33.420 If this container crashes for any reason 01:33.420 --> 01:36.540 or if it needs to be recreated for any reason, 01:36.540 --> 01:38.010 no problem whatsoever. 01:38.010 --> 01:39.622 The old container will fall away 01:39.622 --> 01:41.580 and the new one can connect 01:41.580 --> 01:44.730 to that persistent volume that exists outside the pod. 01:44.730 --> 01:46.410 Now, let's consider the other case. 01:46.410 --> 01:47.940 The case in which maybe a pod 01:47.940 --> 01:49.800 needs to be deleted or recreated 01:49.800 --> 01:53.220 for some fashion, for some reason, excuse me. 01:53.220 --> 01:54.210 So we can kind of imagine 01:54.210 --> 01:58.623 that if this pod crashes entirely and gets recreated, 02:00.420 --> 02:03.090 no problem whatsoever, the old pod falls away, 02:03.090 --> 02:05.550 it completely disappears but the persistent volume 02:05.550 --> 02:07.530 is still going to stick around. 02:07.530 --> 02:08.820 When the new pod is created 02:08.820 --> 02:10.980 with a new copy of pod Postgres, 02:10.980 --> 02:12.390 that container is going to be able 02:12.390 --> 02:14.820 to connect to that persistent volume 02:14.820 --> 02:17.280 that exists outside of the pod. 02:17.280 --> 02:19.980 So that's a big difference between a normal volume 02:19.980 --> 02:21.270 and a persistent volume. 02:21.270 --> 02:24.000 Essentially, we're talking about the life cycle 02:24.000 --> 02:25.530 of the volume itself. 02:25.530 --> 02:26.460 With a normal volume, 02:26.460 --> 02:28.350 it's tied to the life cycle of the pod. 02:28.350 --> 02:29.520 With a persistent volume, 02:29.520 --> 02:31.230 it's going to last for all time, 02:31.230 --> 02:32.850 or essentially until you and I, 02:32.850 --> 02:34.770 as developers, or as the administrators, 02:34.770 --> 02:37.020 decide to delete it for some reason. 02:37.020 --> 02:39.510 But with a persistent volume, we can recreate a container, 02:39.510 --> 02:41.640 we can recreate a pod, no problem. 02:41.640 --> 02:43.440 The volume is still going to stick around 02:43.440 --> 02:46.200 with all the data that you would expect to have. 02:46.200 --> 02:47.520 All right, So that's the differences 02:47.520 --> 02:49.800 between a persistent volume and a volume. 02:49.800 --> 02:51.570 So let's take another quick break right here 02:51.570 --> 02:52.403 and we'll talk about 02:52.403 --> 02:54.900 what the differences are between a persistent volume 02:54.900 --> 02:56.850 and a persistent volume claim. 02:56.850 --> 02:59.643 So, quick pause and I'll catch you in just a second.