22:
243:
capability some virtualization suites provide. In true failover, the host may have suddenly completely failed, which precludes the latest state of the VM having been copied to the backup host. However, the backup host has everything except for the very latest changes, and may indeed be able to
172:
systems are affected. Virtualization is far more frequently used with network services and user applications, and these can generally tolerate the brief delays which may be involved. The perceived impact, if any, is similar to a longer-than-usual
230:
Note that in practice, regular maintenance operations are required to "merge down" the snapshot stack into a more manageable number of files, to improve performance and optimize storage (redundant overwrites are merged out).
226:
Ideally, the administrative scripts resume backup operations, the new host becomes the primary, and the previous host now receives the backup copies, readying it for a subsequent migration operation.
220:
Since this new current state consists only of changes made since the last backup synchronization, for many applications there is very little to transfer, and this happens very quickly.
211:
Since the older overlays are read-only, they are safe to copy to another machine—the backup host. This is done at regular intervals, and each overlay need only be copied once.
208:
Each new snapshot adds a differential overlay file to the top of a stack that, as a whole, fully describes the machine. Only the topmost overlay can be written to.
39:
297:
86:
58:
185:
The actual process is heavily dependent on the particular virtualization package in use, but in general, the process is as follows:
105:
264:
65:
43:
72:
292:
190:
54:
32:
174:
214:
When a migration operation is requested, the virtual machine is paused, and its current state is saved to disk.
201:, and its virtual peripherals) are taken in the background by the hypervisor, or by a set of administrative
168:). In practice, there is always some minor pause in availability, though it may be low enough that only
202:
79:
156:
virtual machine is moved from one physical host to another, with little or no disruption in service.
247:
Because the operations are so similar, systems that provide one capability may provide the other.
164:
Ideally, the process is completely transparent, resulting in no disruption of service (or
127:
169:
148:
119:
286:
21:
135:
194:
240:
165:
265:"Sun Brings 'Teleportation' to VirtualBox Virtualization Software"
217:
These new, final overlay files are transferred to the backup host.
223:
The hypervisor on the new host resumes the guest virtual machine.
126:
simulation of an entire computer is actually merely a software
198:
15:
244:
resume operation from its last known coherent state.
46:. Unsourced material may be challenged and removed.
8:
106:Learn how and when to remove this message
256:
7:
44:adding citations to reliable sources
14:
20:
298:Fault-tolerant computer systems
55:"Migration" virtualization
31:needs additional citations for
1:
239:Migration is similar to the
152:) is the process by which a
314:
193:of the VM (its simulated
267:. eWeek.com. 30 Nov 2009
235:Relation to failover
40:improve this article
293:Computer networking
160:Subjective effects
130:(VM) running on a
118:In the context of
181:Objective effects
134:computer under a
116:
115:
108:
90:
305:
277:
276:
274:
272:
261:
146:, also known as
111:
104:
100:
97:
91:
89:
48:
24:
16:
313:
312:
308:
307:
306:
304:
303:
302:
283:
282:
281:
280:
270:
268:
263:
262:
258:
253:
237:
183:
162:
142:(also known as
128:virtual machine
112:
101:
95:
92:
49:
47:
37:
25:
12:
11:
5:
311:
309:
301:
300:
295:
285:
284:
279:
278:
255:
254:
252:
249:
236:
233:
228:
227:
224:
221:
218:
215:
212:
209:
206:
182:
179:
170:hard real-time
161:
158:
149:live migration
120:virtualization
114:
113:
28:
26:
19:
13:
10:
9:
6:
4:
3:
2:
310:
299:
296:
294:
291:
290:
288:
266:
260:
257:
250:
248:
245:
242:
234:
232:
225:
222:
219:
216:
213:
210:
207:
204:
200:
197:storage, its
196:
192:
188:
187:
186:
180:
178:
176:
171:
167:
159:
157:
155:
151:
150:
145:
144:teleportation
141:
137:
133:
129:
125:
121:
110:
107:
99:
96:December 2014
88:
85:
81:
78:
74:
71:
67:
64:
60:
57: –
56:
52:
51:Find sources:
45:
41:
35:
34:
29:This article
27:
23:
18:
17:
269:. Retrieved
259:
246:
238:
229:
184:
163:
153:
147:
143:
139:
131:
123:
117:
102:
93:
83:
76:
69:
62:
50:
38:Please help
33:verification
30:
287:Categories
251:References
136:hypervisor
122:, where a
66:newspapers
195:hard disk
191:snapshots
140:migration
241:failover
189:Regular
166:downtime
203:scripts
177:delay.
154:running
80:scholar
199:memory
175:kernel
82:
75:
68:
61:
53:
271:7 May
124:guest
87:JSTOR
73:books
273:2021
132:host
59:news
42:by
289::
138:,
275:.
205:.
109:)
103:(
98:)
94:(
84:·
77:·
70:·
63:·
36:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
