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https://issues.apache.org/jira/browse/FLINK-28539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17566618#comment-17566618
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Yanfei Lei edited comment on FLINK-28539 at 10/31/22 4:20 AM:
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hi [~usamj] , +1 for enabling {{LevelCompactionDynamicLevelBytes}} for
FLASH_SSD_OPTIMIZED. And now it's also possible to use
{{LevelCompactionDynamicLevelBytes}} by configuring
"RocksDBConfigurableOptions.USE_DYNAMIC_LEVEL_SIZE: true" manually.
{quote}There is also an argument to be made to also disable it for
SPINNING_DISK options as it could give increased read/write performance [2]
{quote}
As the doc says, "Spinning disks usually provide much lower random read
throughput than flash. If you use level-based compaction, use
options.level_compaction_dynamic_level_bytes=true." I don't see it suggesting
disabling {{LevelCompactionDynamicLevelBytes?}}
was (Author: yanfei lei):
hi [~usamj] , you can use `setLevelCompactionDynamicLevelBytes` for
FLASH_SSD_OPTIMIZED by configuring
"RocksDBConfigurableOptions.USE_DYNAMIC_LEVEL_SIZE: true" manually.
{quote}There is also an argument to be made to also disable it for
SPINNING_DISK options as it could give increased read/write performance [2]
{quote}
Currently, the default value of PREDEFINED_OPTIONS is [empty in
Flink|https://github.com/apache/flink/blob/master/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBOptions.java#L77-L90],
users can choose whether to open according to their own situation.
> Enable CompactionDynamicLevelBytes in FLASH_SSD_OPTIMIZED
> ---------------------------------------------------------
>
> Key: FLINK-28539
> URL: https://issues.apache.org/jira/browse/FLINK-28539
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / State Backends
> Reporter: Usamah Jassat
> Priority: Minor
>
> Investigating the RocksDB predefined options I see that
> `setLevelCompactionDynamicLevelBytes` is set for SPINNING_DISK options but
> not FLASH_SSD_OPTIMIZED.
>
> From my research it looks like this change would improve the Space
> Amplification of RocksDB [1] (which can also lead to a trade-off from
> read/write amplification [2]). It makes sense to me that this feature should
> be enabled for SSD's as they tend to have less space compared to their HDD
> counterparts.
> There is also an argument to be made to also disable it for SPINNING_DISK
> options as it could give increased read/write performance [2]
> [1] [http://rocksdb.org/blog/2015/07/23/dynamic-level.html]
> [2]
> [https://github.com/EighteenZi/rocksdb_wiki/blob/master/RocksDB-Tuning-Guide.md#amplification-factors]
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