Impact of changing disk block size and ROS file size on vertica performance

Arvind_Kumar

Hi ,

 

What would be impact on vertica performnace if i increase or decrease disk block size.

 

Vertica recommends that the disk block size be 4096 bytes what if i will change it to 8192 or reduce to 2048.

 

How i can change minimum and maximum ROS size file on disk?

 

Will ROS bundling combine multiple files into one file on disk?

 

Please help.

Adrian_Oprea_1

Hi ,

 

 Every application uses a different I/O request size and based on how big the request size is, it can have pretty good impact on storage performance.

 In Vertica case the db server was designed to make larger requestes as compared with RDBMS like Oracle, SQL Server, MySQL etc..   

 

See this article to get a better grasp in how block size influences your applicaiton.

https://www.ibm.com/developerworks/library/l-linux-on-4kb-sector-disks/

 

tharanga

>>How i can change minimum and maximum ROS size file on disk?

 

The sizes of files are determined by many factors, you cannot control minimum/maximum sizes. Vertica attempts to be in GB range, but many factors such as partitioing and local segementation (if enabled, disabled by default) could create many small files.

>> Will ROS bundling combine multiple files into one file on disk?

It depends. If your storage containers are small (having files smaller than 1MB) then Vertica will bundle such small files in a storage container to a bundle.

A good example is a wide column table. Let's say you have 100 column table and load a small dataset. If this attempts to create smaller files per column, instead of creating 100's of them, Vertica will write out just one bundle. This feature is available from 7.2 onwards and it's by default ON.

(You can reduce the 1MB size threshold Vertica uses for bundling, but not recommended).