Benchmark a Redis on Flash Enabled Database
Redis on Flash (RoF) on Redis Enterprise Software (RS) lets you use more cost-effective Flash memory as a RAM extension for your database. But what does the performance look like as compared to an all-RAM RS database?
The simple scenarios on this page show you how you can get performance results with the free RS trial version. If you would like assistance with your evaluation or need to test a larger cluster, we'd be happy to help.
Benchmark and Performance Test Considerations
For our testing, let's configure a Redis Enterprise Software cluster with the trial version and use memtier_benchmark to evaluate the performance of a Redis on Flash enabled database in these scenarios:
- Without replication: 4 master shards
- With replication: 2 master and 2 slave shards
While it concentrates on RoF, you can also use these steps to evaluate RS without RoF.
The Redis Enterprise Software trial version lets you use up to 4 Redis shards with multiple combinations of databases, such as:
- 4 databases with 1 master shard each
- 2 highly available databases with replication, where each database has 1 master shard and 1 slave shard
- 1 non-replicated clustered database with 4 master shards
- 1 highly available and clustered database with 2 master shards and 2 slave shards
Test Environment and RS Cluster Setup
For the test environment, you must:
- Create a three-node RS cluster.
- Prepare the flash memory.
- Setup the load generation tool.
Creating a three-node RS cluster
For this performance test, you need at least a three-node RS cluster. You can run all of these tests on Amazon AWS with these hosts:
- 2 x i3.2xlarge (8 vCPU, 61 GiB RAM, up to 10GBit, 1.9TB NMVe SSD) - Used for serving RoF data
- 1 x m4.large - Used as a quorum node
For instructions on how to install RS and set up a cluster, go to either:
For the tests we use a quorum node in the cluster to keep costs down on AWS instance usage, but still keep the minimum 3 nodes in the cluster that RS needs in case a node fails. The quorum node can be on a less powerful instance type (m4.large) as it will not have shards on it or take traffic.
The main reason to use a i3.2xlarge instance is to use NVMe SSDs. Those SSDs are what RoF will combine with RAM to host the database on. If you run these tests in another environment (such as on-premise), you must use NVMe SSDs to see the performance benefits of RoF.
Preparing the Flash Memory
After you install RS on the nodes,
the flash memory attached to the i3.2xlarge instances must be prepared and formatted with the
Setting up the Load Generation Tool
The memtier_benchmark load generator tool generates the load on the RoF databases. To use this tool, install RS on a dedicated instance that is not part of the RS cluster but is in the same region/zone/subnet of your cluster. We recommend that you use a relatively powerful instance to avoid bottlenecks at the load generation tool itself.
For these tests, the load generation host uses a c4.8xlarge instance type.
Database Configuration Parameters
Create a Redis on Flash test database
You can use the RS web UI to create a test database. We recommend that you use a separate database for each test case with these requirements:
|Parameter||With replication||Without replication||Description|
|Name||test-1||test-2||The name of the test database|
|Memory limit||100 GB||100 GB||The memory limit refers to RAM+Flash, aggregated across all the shards of the database, including master and slave shards.|
|RAM limit||0.3||0.3||RoF always keeps the Redis keys and Redis dictionary in RAM and additional RAM is required for storing hot values. For the purpose of these tests 30% RAM was calculated as an optimal value.|
|Replication||Enabled||Disabled||A database with no replication has only master shards. A database with replication has master and slave shards.|
|Data persistence||None||None||No data persistence is needed for these tests.|
|Database clustering||Enabled||Enabled||A clustered database consists of multiple shards.|
|Number of (master) shards||2||4||Shards are distributed as follows:
- With replication: 1 master shard and 1 slave shard on each node
- Without replication: 2 master shards on each node
|Other parameters||Default||Default||Keep the default values for the other configuration parameters.|
Populate the benchmark dataset
The memtier_benchmark load generation tool populates the database. To populate the database with N items of 500 Bytes each in size, on the load generation instance run:
$ memtier_benchmark -s $DB_HOST -p $DB_PORT --hide-histogram --key-maximum=$N -n allkeys -d 500 --key-pattern=P:P --ratio=1:0
Setup a test database with these values:
|The fully qualified name of the endpoint or the IP shown in the RS database configuration|
|The endpoint port shown in you RS database configuration|
|Number of items
|With replication: 75 Million
Without replication: 150 Million
Centralize the Keyspace
To create about 20.5 million items in RAM for your highly available clustered database with 75 million items, run:
$ memtier_benchmark -s $DB_HOST -p $DB_PORT --hide-histogram --key-minimum=27250000 --key-maximum=47750000 -n allkeys --key-pattern=P:P --ratio=0:1
You can see the Values in RAM metric on the metrics page of your database in the RS web UI to validate the test.
To create 41 million items in RAM without replication enabled and 150 million items, run:
$ memtier_benchmark -s $DB_HOST -p $DB_PORT --hide-histogram --key-minimum=54500000 --key-maximum=95500000 -n allkeys --key-pattern=P:P --ratio=0:1
We recommend that you do a dry run and double check the RAM Hit Ratio on the metrics screen in the RS web UI before you write down the test results.
To test RoF with an 85% RAM Hit Ratio, run:
$ memtier_benchmark -s $DB_HOST -p $DB_PORT --pipeline=11 -c 20 -t 1 -d 500 --key-maximum=75000000 --key-pattern=G:G --key-stddev=5125000 --ratio=1:1 --distinct-client-seed --randomize --test-time=600 --run-count=1 --out-file=test.out
Here is the command for 150 million items:
$ memtier_benchmark -s $DB_HOST -p $DB_PORT --pipeline=24 -c 20 -t 1 -d 500 --key-maximum=150000000 --key-pattern=G:G --key-stddev=10250000 --ratio=1:1 --distinct-client-seed --randomize --test-time=600 --run-count=1 --out-file=test.out
|Access pattern (--key-pattern) and standard deviation (--key-stddev)||Controls the RAM Hit ratio after the centralization process is complete|
|Number of threads (-t and -c)||Controls how many connections are opened to the database, whereby the number of connections is the number of threads multiplied by the number of connections per thread (-t) and number of clients per thread (-c)|
|Pipelining (--pipeline)||Pipelining allows you to send multiple requests without waiting for each individual response (-t) and number of clients per thread (-c)|
|Read\write ratio (--ratio)||A value of 1:1 means that you have the same number of write operations as read operations (-t) and number of clients per thread (-c)|
Monitor the test results
You can either monitor the results in the metrics tab of the RS Web UI or with the memtier_benchmark output. The memtier_benchmark results include the network latency between the load generator instance and the cluster instances. The metrics shown in the RS web UI do not include network latency.
You should expect to see an average throughput of:
- Around 160,000 ops/sec when testing without replication (i.e. 4 master shards)
- Around 115,000 ops/sec when testing with enabled replication (i.e. 2 master and 2 slave shards)
In both cases the average latency should be sub-millisecond.