# WiredTiger Compression Degradation

**URL:** <https://forums.percona.com/t/wiredtiger-compression-degradation/6530>\
**Category:** Percona Server for MongoDB\
**Created:** [August 23, 2018, 2:04am UTC](https://forums.percona.com/t/wiredtiger-compression-degradation/6530 "2018-08-23T02:04:12Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![tanveermadan](https://avatars.discourse-cdn.com/v4/letter/t/76d3ee/32.png) [@tanveermadan](https://forums.percona.com/u/tanveermadan)\
**Post date:** [August 23, 2018, 2:04am UTC](https://forums.percona.com/t/wiredtiger-compression-degradation/6530/1 "2018-08-23T02:04:12Z")

</div>

Hi,

We recently upgraded out MongoDB from community version 3.4.14 to 4.0.1

We see that the compression ratio differs for the same type of data between the version

Hence we did a test and found that compression ratio drastically fell for 3.6+ [TABLE]  
[TR]  
[TD]Version[/TD]  
[TD]Raw size[/TD]  
[TD]Storage size[/TD]  
[TD]Comp Ratio[/TD]  
[/TR]  
[TR]  
[TD]4.0[/TD]  
[TD]10378066324[/TD]  
[TD]1594658816[/TD]  
[TD]6.5x[/TD]  
[/TR]  
[TR]  
[TD]3.6[/TD]  
[TD]10378066324[/TD]  
[TD]1599205376[/TD]  
[TD]6.49x[/TD]  
[/TR]  
[TR]  
[TD]3.4[/TD]  
[TD]10378066324[/TD]  
[TD]634499072[/TD]  
[TD]16.35x[/TD]  
[/TR]  
[/TABLE]

Can you please suggest if any changes has to be made in the configuration of MongoDB or WiredTiger?

Below is the wired tiger configuration we are using

wiredTiger:  
collectionConfig:  
blockCompressor: zlib  
engineConfig:  
directoryForIndexes: true  
journalCompressor: none  
cacheSizeGB: 40  
configString: “eviction\_dirty\_target=60, eviction\_dirty\_trigger=80, eviction=(threads\_min=20,threads\_max=20)”

Thanks,

Tanveer