Database Reference
In-Depth Information
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 65536 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
File Limit Settings
You will also need to ensure that Cassandra isn't being limited by the number
of files allowed by the kernel. This can be done by giving a larger value to
fs.file-max
in your
sysctl
settings. A good setting for this is 1,048,576.
In addition to changing the
sysctl
setting, you will need to raise the open file
limit for the system. By adding the two lines in
Listing 6.7
to your /etc/security/
limits.conf, you should be able to give Cassandra enough room to operate under
normal and heavy loads.
Listing 6.7
/etc/security/limits.conf Settings for Allowing Additional Open
Files
* soft
nofile
16,384
* hard
nofile
32,768
Solid-State Drives
Although Cassandra's storage engine was optimized for spinning disks, you can
still benefit a lot from the use of SSDs. This is evident because most modern SATA
drives are best at sequential operations. Seek times are limited by the time it takes
the drive to rotate. As good throughput as SATA drives get (a 7,200rpm drive typ-
ically gets around 125MB/s), solid-state drives are just better at it. They usually
get about 250MB/s read and 205MB/s write throughput.
Since Cassandra writes sequentially and uses streaming write patterns, it min-
imizes the effects of write amplification associated with SSDs. Write amplification
is a concept associated with solid-state drives where the amount of physical in-
formation written is a multiple of the logical amount intended to be written. This
means that Cassandra does a good job of giving normal consumer-level SSDs a
longer life span.
