Details
-
Question
-
Resolution: Done
-
Major - P3
-
None
-
None
-
None
-
None
Description
We're running a mongodb 4.2 with zstd collection block compression. The oplog is set to oplogSizeMB: 3000000 MB, but the actual collection size is ~350GB. It's like 10X compression ration. According to https://source.wiredtiger.com/3.1.0/compression.html, the default compression ration for zstd is 3. What explains the big difference between the data size and total size of oplog collection?
PRIMARY> db.getReplicationInfo()
|
{
|
"logSizeMB" : 3000000, |
"usedMB" : 2996131.66, |
"timeDiff" : 123687, |
"timeDiffHours" : 34.36, |
"tFirst" : "Sun Feb 21 2021 01:55:32 GMT-0700 (MST)", |
"tLast" : "Mon Feb 22 2021 12:16:59 GMT-0700 (MST)", |
"now" : "Mon Feb 22 2021 12:16:59 GMT-0700 (MST)" |
}
|
|
|
PRIMARY> db.oplog.rs.totalSize()
|
379049607168
|
|
|
PRIMARY> db.oplog.rs.dataSize()
|
NumberLong("3118230005927") |