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https://issues.apache.org/jira/browse/CASSANDRA-10419?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Shook updated CASSANDRA-10419:
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Description:
With JBOD and several smaller disks, like SSDs at 1.2 TB or lower, it is
possible to run out of space prematurely. With a sufficient ingestion rate,
disk selection logic seems to overselect on certain JBOD targets. This causes a
premature C* shutdown when there is a significant amount of space left. With
DTCS, for example, it should be possible to utilize over 90% of the available
space with certain settings. However in the scenario I tested, only about 50%
was utilized, before a filesystem full error. (see below). It is likely that
this is a scheduling challenge between high rates of ingest and smaller data
directories. It would be good to use an anticipatory model if possible to more
carefully select compaction targets according to fill rates. As well, if the
largest sstable that can be supported is constrained by the largest JBOD
extent, we should make that visible to the compaction logic where possible.
The attached image shows a test with 12 1.2TB JBOD data directories. At the
end, the utilizations are:
59GiB, 83GiB, 83GiB, 97GiB, 330GiB, 589GiB, 604GiB, 630GiB, 697GiB, 1.055TiB,
1.083TB, 1092TiB,
was:
With JBOD and several smaller disks, like SSDs at 1.2 TB or lower, it is
possible to run out of space prematurely. With a sufficient ingestion rate,
disk selection logic seems to overselect on certain JBOD targets. This causes a
premature C* shutdown when there is a significant amount of space left. With
DTCS, for example, it should be possible to utilize over 90% of the available
space with certain settings. However in the scenario I tested, only about 50%
was utilized, before a filesystem full error. (see below). It is likely that
this is a scheduling challenge between high rates of ingest and smaller data
directories. It would be good to use an anticipatory model if possible to more
carefully select compaction targets according to fill rates.
The attached image shows a test with 12 1.2TB JBOD data directories. At the
end, the utilizations are:
59GiB, 83GiB, 83GiB, 97GiB, 330GiB, 589GiB, 604GiB, 630GiB, 697GiB, 1.055TiB,
1.083TB, 1092TiB,
> Make JBOD compaction and flushing more robust
> ---------------------------------------------
>
> Key: CASSANDRA-10419
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10419
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Shook
> Attachments: timeseries-study-overview-jbods.png
>
>
> With JBOD and several smaller disks, like SSDs at 1.2 TB or lower, it is
> possible to run out of space prematurely. With a sufficient ingestion rate,
> disk selection logic seems to overselect on certain JBOD targets. This causes
> a premature C* shutdown when there is a significant amount of space left.
> With DTCS, for example, it should be possible to utilize over 90% of the
> available space with certain settings. However in the scenario I tested, only
> about 50% was utilized, before a filesystem full error. (see below). It is
> likely that this is a scheduling challenge between high rates of ingest and
> smaller data directories. It would be good to use an anticipatory model if
> possible to more carefully select compaction targets according to fill rates.
> As well, if the largest sstable that can be supported is constrained by the
> largest JBOD extent, we should make that visible to the compaction logic
> where possible.
> The attached image shows a test with 12 1.2TB JBOD data directories. At the
> end, the utilizations are:
> 59GiB, 83GiB, 83GiB, 97GiB, 330GiB, 589GiB, 604GiB, 630GiB, 697GiB, 1.055TiB,
> 1.083TB, 1092TiB,
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