Shulou(Shulou.com)06/01 Report--

1. Optimize the pre-reading

The BLOCKDEV command of LINUX is used to reduce the pre-read size and reduce the occupation of useless data in memory, thus optimizing IO performance.

RA represents the pre-read size (sector). The recommended value is 16-32. If the document is small, the pre-read value can be smaller before mongodb restart takes effect after modification.

Pre-read default 256 sectors with a size of 128K

Many of the mongodb are random visits, and the readhead should be set smaller. For example, you only read 10k, but you read 128k.

Root@db3-198 report report # blockdev

RO RA SSZ BSZ StartSec Size Device

Rw 128 512 4096 0 800166076416 / dev/sda

Rw 128 512 1024 2048 524288000 / dev/sda1

Rw 128 512 4096 1026048 799639863296 / dev/sda2

Rw 256 512 4096 0 53687091200 / dev/dm-0

Rw 256 512 4096 0 33822867456 / dev/dm-1

Rw 256 512 4096 0 712125710336 / dev/dm-2

Use the following command

Blockdev-setra 128 / dev/sda2

Represents a pre-read size of 128 to 512 bytes / sector = 64K

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