i use kafka cluster using by docker container
kafka-1:
image: confluentinc/cp-kafka:latest
depends_on:
- zookeeper-1
- zookeeper-2
- zookeeper-3
ports:
- "29092:29092"
environment:
KAFKA_BROKER_ID: 1
KAFKA_ZOOKEEPER_CONNECT: zookeeper-1:2181,zookeeper-2:2181,zookeeper-3:2181
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka-1:9092,PLAINTEXT_HOST://61.125.196.42:29092
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
KAFKA_TRANSACTION_STATE_LOG_REPLICATION_FACTOR: 1
KAFKA_TRANSACTION_STATE_LOG_MIN_ISR: 1
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
KAFKA_DEFAULT_REPLICATION_FACTOR: 2
and KAKFA_ADVERTISED_LISTENERS is host for external consumer,producer.
in this setting, what is difference PLAINTEXT and PLAINTEXT_HOST?
First only passed data on 61.125.196.42:29092 not kafka-1:9092.
It's just a name.
The only requirement for the host one is that it needs to be a name in the security protocol mapping since it's not a builtin protocol.
The difference is that one is for external clients, as you said. The other is only within the Docker network where kafka-1 DNS name is actually resolvable, similar to your Zookeepers
Refer Connect to Kafka running in Docker
Related
I'm in a bit of trouble trying to run provectus/kafka-ui docker containers.
I have a collection of servers all running on the same internal network. On three of these servers a Kafka cluster is implemented (Zookeeper and Broker). The structure of the Broker looks like the following:
192.168.0.237:9092
192.168.0.7:9092
192.168.0.54:9092
The problem is that there is no Docker instance running on any of these servers.
What I would like to achieve now is to install provectus/kafka-ui on another server (192.168.0.8) and make it accessible from within the network via a specific port (e.g. 8080).
I have found a few docker-compose.yml examples https://github.com/provectus/kafka-ui. However, the Kafka cluster is created on the same server as kafka-ui. In my case, the cluster already exists and only kafka-ui is missing on another server. Can anyone tell me how I can adapt the docker-compose.yml so that kafka-ui can be installed on 192.168.0.8 and made available from outside via port 8080?
Kind regards and thanks in advance
version: '3'
services:
kafka-ui:
container_name: kafka-ui
image: provectuslabs/kafka-ui:latest
ports:
- 8080:8080
depends_on:
- zookeeper
- kafka1
environment:
KAFKA_CLUSTERS_0_NAME: local
KAFKA_CLUSTERS_0_BOOTSTRAPSERVERS: kafka1:19091
KAFKA_CLUSTERS_0_ZOOKEEPER: zookeeper:2181
KAFKA_CLUSTERS_0_JMXPORT: 9997
SERVER_SERVLET_CONTEXT_PATH: /kafkaui
AUTH_TYPE: "LOGIN_FORM"
SPRING_SECURITY_USER_NAME: test_user
SPRING_SECURITY_USER_PASSWORD: test
zookeeper:
image: confluentinc/cp-zookeeper:5.2.4
hostname: zookeeper
ports:
- "2181:2181"
environment:
ZOOKEEPER_CLIENT_PORT: 2181
volumes:
- ./data/zookeeper/data:/data
- ./data/zookeeper/datalog:/datalog
kafka1:
image: confluentinc/cp-kafka:5.3.1
hostname: kafka1
ports:
- "9091:9091"
environment:
KAFKA_ADVERTISED_LISTENERS: LISTENER_DOCKER_INTERNAL://kafka1:19091,LISTENER_DOCKER_EXTERNAL://${DOCKER_HOST_IP:-127.0.0.1}:9091
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: LISTENER_DOCKER_INTERNAL:PLAINTEXT,LISTENER_DOCKER_EXTERNAL:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: LISTENER_DOCKER_INTERNAL
KAFKA_ZOOKEEPER_CONNECT: "zookeeper:2181"
KAFKA_BROKER_ID: 1
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 2
KAFKA_AUTO_CREATE_TOPICS_ENABLE: "False"
volumes:
- ./data/kafka1/data:/var/lib/kafka/data
depends_on:
- zookeeper
kafka2:
image: confluentinc/cp-kafka:5.3.1
hostname: kafka2
ports:
- "9092:9092"
environment:
KAFKA_ADVERTISED_LISTENERS: LISTENER_DOCKER_INTERNAL://kafka2:19092,LISTENER_DOCKER_EXTERNAL://${DOCKER_HOST_IP:-127.0.0.1}:9092
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: LISTENER_DOCKER_INTERNAL:PLAINTEXT,LISTENER_DOCKER_EXTERNAL:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: LISTENER_DOCKER_INTERNAL
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
KAFKA_BROKER_ID: 2
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 2
KAFKA_AUTO_CREATE_TOPICS_ENABLE: "False"
volumes:
- ./data/kafka2/data:/var/lib/kafka/data
depends_on:
- zookeeper
kafka3:
image: confluentinc/cp-kafka:5.3.1
hostname: kafka3
ports:
- "9093:9093"
environment:
KAFKA_ADVERTISED_LISTENERS: LISTENER_DOCKER_INTERNAL://kafka3:19093,LISTENER_DOCKER_EXTERNAL://${DOCKER_HOST_IP:-127.0.0.1}:9093
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: LISTENER_DOCKER_INTERNAL:PLAINTEXT,LISTENER_DOCKER_EXTERNAL:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: LISTENER_DOCKER_INTERNAL
KAFKA_ZOOKEEPER_CONNECT: "zookeeper:2181"
KAFKA_BROKER_ID: 3
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 2
KAFKA_AUTO_CREATE_TOPICS_ENABLE: "False"
volumes:
- ./data/kafka3/data:/var/lib/kafka/data
depends_on:
- zookeeper
kafdrop:
image: obsidiandynamics/kafdrop
restart: "no"
ports:
- "9000:9000"
environment:
KAFKA_BROKERCONNECT: "kafka1:19091"
depends_on:
- kafka1
- kafka2
- kafka3
You don't need Docker on the Kafka brokers... Also, IP doesn't really matter as long as advertised.listeners on Kafka is setup correctly.
Remove the three Kafka containers, the Zookeeper container, and simply change these to your actual Kafka brokers + Zookeeper servers
KAFKA_CLUSTERS_0_BOOTSTRAPSERVERS
KAFKA_CLUSTERS_0_ZOOKEEPER
Also remove kafdrop? Since it's basically another UI with overlapping features.
Or, install pnpm and Java, and you can run the UI + API without Docker, just like you're doing with Kafka.
https://github.com/provectus/kafka-ui/tree/master/kafka-ui-react-app
I am new to kafka, i tried to setup my first cluster on a vps with Docker-compose. But i still cannot access it from my local pc ( outside the host ).
here is my docker compose
version: '2'
services:
zookeeper-1:
image: confluentinc/cp-zookeeper:latest
environment:
ZOOKEEPER_CLIENT_PORT: 2181
ZOOKEEPER_TICK_TIME: 2000
ports:
- 22181:2181
zookeeper-2:
image: confluentinc/cp-zookeeper:latest
environment:
ZOOKEEPER_CLIENT_PORT: 2181
ZOOKEEPER_TICK_TIME: 2000
ports:
- 32181:2181
kafka-1:
image: confluentinc/cp-kafka:latest
depends_on:
- zookeeper-1
- zookeeper-2
ports:
- 29092:29092
environment:
KAFKA_BROKER_ID: 1
KAFKA_ZOOKEEPER_CONNECT: zookeeper-1:2181,zookeeper-2:2181
KAFKA_LISTENERS: EXTERNAL_SAME_HOST://:29092,EXTERNAL_DIFFERENT_HOST://:29093,INTERNAL://:9092
KAFKA_ADVERTISED_LISTENERS: INTERNAL://kafka:9092,EXTERNAL_SAME_HOST://localhost:29092,EXTERNAL_DIFFERENT_HOST://XXX.XXX.XXX.XXX:29093
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: INTERNAL:PLAINTEXT,EXTERNAL_SAME_HOST:PLAINTEXT,EXTERNAL_DIFFERENT_HOST:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: INTERNAL
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
kafka-2:
image: confluentinc/cp-kafka:latest
depends_on:
- zookeeper-1
- zookeeper-2
ports:
- 39092:39092
environment:
KAFKA_BROKER_ID: 2
KAFKA_ZOOKEEPER_CONNECT: zookeeper-1:2181,zookeeper-2:2181
KAFKA_LISTENERS: EXTERNAL_SAME_HOST://:39092,EXTERNAL_DIFFERENT_HOST://:39093,INTERNAL://:9093
KAFKA_ADVERTISED_LISTENERS: INTERNAL://kafka:9093,EXTERNAL_SAME_HOST://localhost:39092,EXTERNAL_DIFFERENT_HOST://XXX.XXX.XXX.XXX:39093
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: INTERNAL:PLAINTEXT,EXTERNAL_SAME_HOST:PLAINTEXT,EXTERNAL_DIFFERENT_HOST:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: INTERNAL
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
I searched in the logs and i found that there is no available brokers ( always 0 ) because the server couldn't connect to "kafka:9092" AND Zookeeper keep failing to connect to the brokers.
[2022-04-13 14:56:59,422] WARN Session 0x0 for sever My-vps-URL/XXX.XXX.XXX.XXX:2181, Closing socket connection. Attempting reconnect except
it is a SessionExpiredException. (org.apache.zookeeper.ClientCnxn)
org.apache.zookeeper.ClientCnxn$SessionTimeoutException: Client session timed out, have not
heard from server in 30006ms for session id 0x0
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1258)
KeeperErrorCode = ConnectionLoss for /brokers/ids
How can i fix this ?
Note that i tried a similar config with a different docker image ( bitnami's ), and with different cluster config ( 1 zookeeper 1 broker ) and it still doesn't work.
You have a Zookeeper error because you are running an even number of them. The number of Zookeepers doesn't need to match the number of brokers, and it should be an odd number of them, only, up to 7 max. You also shouldn't need ports on the Zookeeper servers.
For your Kafka Connection,
KAFKA_LISTENERS needs to include the IP of 0.0.0.0 to allow for the server to bind on all interfaces
You need to expose port 29093 and 39093 since those are your "different host" settings. You currently only have ports to connect from the same machine.
your clients need to connect to the EXTERNAL_DIFFERENT_HOST address you've set, not kafka:9092
Further reading - Connect to Kafka running in Docker
tried a similar config with a different docker image ( bitnami's )
That image has different variables, but same basic answer as above.
different cluster config ( 1 zookeeper 1 broker )
There is little benefit of running multiple of each of those on the same machine, so I suggest trying to get that configuration working, first.
I'm new to Kafka and I'm trying to run a Kafka service on my local machine and use it to transfer some data from one .NET project to another.
I'm using docker-compose.yml file to create two docker containers for zookeeper and Kafka from wurstmeister.
In Kafka definition in environment variables there is KAFKA_ADVERTISED_HOST_NAME which I set to 127.0.0.1.
In docker hub of wurstmeister/kafka says I quote
"modify the KAFKA_ADVERTISED_HOST_NAME in docker-compose.yml to match your docker host IP (Note: Do not use localhost or 127.0.0.1 as the host IP if you want to run multiple brokers.)".
When I set my topic to have more than 1 replica and more than 1 partition I get this message
"Error while executing topic command : Replication factor: 2 larger than available brokers: 1.".
What is the right IP address to define in KAFKA_ADVERTISED_HOST_NAME which will allow me to get more than 1 broker?
version: '2'
services:
zookeeper:
image: wurstmeister/zookeeper
ports:
- "2181:2181"
kafka:
image: wurstmeister/kafka
ports:
- "9092:9092"
environment:
KAFKA_ADVERTISED_HOST_NAME: 127.0.0.1
KAFKA_CREATE_TOPICS: "simpletalk_topic:2:2"
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- /var/run/docker.sock:/var/run/docker.sock
Note - Running multiple brokers on one machine does not provide true fault tolerance.
use it to transfer some data from one .NET project to another
You only need one broker for this.
First, suggest reading https://github.com/wurstmeister/kafka-docker/wiki/Connectivity
KAFKA_ADVERTISED_HOST_NAME is deprecated. Don't use it.
It has been replaced by KAFKA_ADVERTISED_LISTENERS, which can both contain ${DOCKER_HOST_IP:-127.0.0.1} (or your host IP from ifconfig) since this is the IP your client will use (from the host).
Since brokers are clients of themselves, you also need to advertise the container names. And, if you want to containerize your client, those addresses would also be used by your app.
Beyond Kafka networking configs, KAFKA_BROKER_ID needs to be different between each, and your error is suggesting you need to override all the other replication factor broker configs.
All in all.
version: '3'
services:
zookeeper:
image: wurstmeister/zookeeper
kafka-1:
image: wurstmeister/kafka
depends_on: [zookeeper]
ports:
- "9092:9092"
environment:
KAFKA_BROKER_ID: 1
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://${DOCKER_HOST_IP:-127.0.0.1}:9092,PLAINTEXT_INTERNAL://kafka-1:29092
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092,PLAINTEXT_INTERNAL://:29092
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT_INTERNAL:PLAINTEXT,PLAINTEXT:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT_INTERNAL
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
KAFKA_DEFAULT_REPLICATION_FACTOR: 2
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 2
KAFKA_TRANSACTION_STATE_LOG_REPLICATION_FACTOR: 2
kafka-2:
image: wurstmeister/kafka
ports:
- "9093:9093"
environment:
KAFKA_BROKER_ID: 2 # unique
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://${DOCKER_HOST_IP:-127.0.0.1}:9093,PLAINTEXT_INTERNAL://kafka-2:29093
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9093,PLAINTEXT_INTERNAL://:29093
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT_INTERNAL:PLAINTEXT,PLAINTEXT:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT_INTERNAL
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
KAFKA_DEFAULT_REPLICATION_FACTOR: 2
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 2
KAFKA_TRANSACTION_STATE_LOG_REPLICATION_FACTOR: 2
KAFKA_CREATE_TOPICS: "simpletalk_topic:2:2"
depends_on: # ensure this joins the other
- zookeeper
- kafka-1
I'm trying to run a Kafka service on my local machine
Set bootstrap.servers="localhost:9092,localhost:9093"
Further reading - Connect to Kafka running in Docker
Example usage
Note that topic creation doesn't seem to automatically work. You should ideally be using your application to actually create / check topic existence.
$ kcat -b localhost:9093 -L
Metadata for all topics (from broker -1: localhost:9093/bootstrap):
2 brokers:
broker 2 at 127.0.0.1:9093
broker 1 at 127.0.0.1:9092 (controller)
0 topics:
producing some data... and consuming it
$ kcat -b localhost:9093 -t test -o earilest
% Auto-selecting Consumer mode (use -P or -C to override)
hello
world
sample
data
of
no
importance
it should be ip address of your machine.
Linux: use ifconfig command and your IP will be inet <IP_ADDRESS>
in windows you will get this by using ipconfig
I've read a lot of similar subjects but they aren't able to answer my problem here.
Trying to run some short integration tests, I'm using docker-compose 3, a single-node kafka. On client side I'm using Go shopify/sarama to consume / produce
zookeeper:
image: confluentinc/cp-zookeeper:5.2.2
hostname: zookeeper
container_name: zookeeper
ports:
- "2181:2181"
environment:
ZOOKEEPER_CLIENT_PORT: 2181
ZOOKEEPER_TICK_TIME: 2000
kafka:
image: confluentinc/cp-enterprise-kafka:5.2.2
hostname: kafka
container_name: kafka
depends_on:
- zookeeper
ports:
- "29092:29092"
expose:
- 9092
environment:
KAFKA_BROKER_ID: 1
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
KAFKA_LISTENERS: PLAINTEXT://kafka:9092,PLAINTEXT_HOST://localhost:29092
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092,PLAINTEXT_HOST://localhost:29092
KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
I have another container from the docker-compose that will listen to
- "BROKERS_URL=kafka:9092"
the consumer is working just fine:
Sarama consumer up and running. {"brokers": ["kafka:9092"], "topics": ["validated"], "group": "event-service"}
But on the producer part, running directly from my machine:
kafka: client has run out of available brokers to talk to (Is your cluster reachable?)
producer, err := sarama.NewSyncProducer([]string{"http://localhost:29092"}, nil)
...
msg := &sarama.ProducerMessage{
Topic: "validated",
Key: sarama.StringEncoder(""),
Value: sarama.ByteEncoder(payload),
}
partition, offset, err := producer.SendMessage(msg)
...
Nothing weird / extravagante here, but it's not working and I'm confused.
also:
nc -vz localhost 29092
Connection to localhost port 29092 [tcp/*] succeeded!
Instead of
KAFKA_LISTENERS: PLAINTEXT://kafka:9092,PLAINTEXT_HOST://localhost:29092
you need
KAFKA_LISTENERS: PLAINTEXT://kafka:9092,PLAINTEXT_HOST://0.0.0.0:29092
Testing connectivity from my host machine using kafkacat shows that this works:
➜ kafkacat -b localhost:29092 -L
Metadata for all topics (from broker 1: localhost:29092/1):
1 brokers:
broker 1 at localhost:29092 (controller)
0 topics:
This difference is that the listener is binding to all available interfaces (0.0.0.0). With your original configuration it binds to the loopback interface (lo) for localhost, and so only accepts traffic on this and not externally.
I'm running Confluent Docker. I am trying to add more brokers using docker-compose.
(I tried docker-compose scale kafka=3 but didn't work for me.)
This is my docker-compose.yml.
version: '2'
services:
broker:
image: confluentinc/cp-enterprise-kafka:5.3.1
hostname: broker
container_name: broker
depends_on:
- zookeeper
ports:
- "29092:29092"
- "9092:9092"
environment:
KAFKA_BROKER_ID: 1
KAFKA_ZOOKEEPER_CONNECT: 'zookeeper:2181'
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://broker:29092,PLAINTEXT_HOST://localhost:9092
KAFKA_METRIC_REPORTERS: io.confluent.metrics.reporter.ConfluentMetricsReporter
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
KAFKA_GROUP_INITIAL_REBALANCE_DELAY_MS: 0
CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: broker:29092
CONFLUENT_METRICS_REPORTER_ZOOKEEPER_CONNECT: zookeeper:2181
CONFLUENT_METRICS_REPORTER_TOPIC_REPLICAS: 1
CONFLUENT_METRICS_ENABLE: 'true'
CONFLUENT_SUPPORT_CUSTOMER_ID: 'anonymous'
#To add more broker, do I do the following?
KAFKA_BROKER_ID: 2 // just add this?
KAFKA_ZOOKEEPER_CONNECT: 'zookeeper:2181'
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://broker:29092,PLAINTEXT_HOST://localhost:9092
KAFKA_METRIC_REPORTERS: io.confluent.metrics.reporter.ConfluentMetricsReporter
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
KAFKA_GROUP_INITIAL_REBALANCE_DELAY_MS: 0
CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: broker:29092
CONFLUENT_METRICS_REPORTER_ZOOKEEPER_CONNECT: zookeeper:2181
CONFLUENT_METRICS_REPORTER_TOPIC_REPLICAS: 1
CONFLUENT_METRICS_ENABLE: 'true'
CONFLUENT_SUPPORT_CUSTOMER_ID: 'anonymous'
1) To add more brokers, what do I need to add or change in docker-compose.yml?
2) Why does Docker use another port 29092? When I run Kafka in non-docker mode, I just needed one port (9092).
You can't use scale because the broker ids need to be different.
And you're missing this top section from the new service
You need two ports because one allows kafka clients on the host to access Kafka (9092), and the other allows Docker services to reach Kafka (29092).
broker2:
image: confluentinc/cp-enterprise-kafka:5.3.1
hostname: broker2
container_name: broker2
depends_on:
- zookeeper
ports:
- "29192:29092" # technically, this one isn't needed to be mapped from the host
- "9192:9092"
environment:
KAFKA_BROKER_ID: 2
KAFKA_ZOOKEEPER_CONNECT: 'zookeeper:2181'
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://broker:29092,PLAINTEXT_HOST://localhost:9092
KAFKA_METRIC_REPORTERS: io.confluent.metrics.reporter.ConfluentMetricsReporter
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
KAFKA_GROUP_INITIAL_REBALANCE_DELAY_MS: 0
CONFLUENT_METRICS_REPORTER_BOOTSTRAP_SERVERS: broker:29092
CONFLUENT_METRICS_REPORTER_ZOOKEEPER_CONNECT: zookeeper:2181
CONFLUENT_METRICS_REPORTER_TOPIC_REPLICAS: 1
If you really want to run a cluster of brokers, though, the Confluent Helm Charts or Strimzi project would be useful, however running multiple Kafka's on one machine isn't improving any performance (they're sharing the same disk, and taking up more space via replication) or resiliency (it's all on one machine)