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https://issues.apache.org/jira/browse/CASSANDRA-15452?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jon Haddad updated CASSANDRA-15452:
-----------------------------------
Description:
On read heavy workloads Cassandra performs much better when using a low read
ahead setting. In my tests I've seen an 5x improvement in throughput and more
than a 50% reduction in latency. However, I've also observed that it can have
a negative impact on compaction and streaming throughput. It especially
negatively impacts cloud environments where small reads incur high costs in
IOPS due to tiny requests.
# We should investigate using POSIX_FADV_DONTNEED on files we're compacting to
see if we can improve performance and reduce page faults.
# This should be combined with an internal read ahead style buffer that
Cassandra manages, similar to a BufferedInputStream but with our own machinery.
This buffer should read fairly large blocks of data off disk at at time. EBS,
for example, allows 1 IOP to be up to 256KB. A considerable amount of time is
spent in blocking I/O during compaction, reducing the frequency we read from
disk should speed up all sequential I/O operations.
was:
On read heavy workloads Cassandra performs much better when using a low read
ahead setting. In my tests I've seen an 5x improvement in throughput and more
than a 50% reduction in latency. However, I've also observed that it can have
a negative impact on compaction and streaming throughput. It especially
negatively impacts cloud environments where small reads incur high costs in
IOPS due to tiny requests.
# We should investigate using POSIX_FADV_DONTNEED on files we're compacting to
see if we can improve performance and reduce page faults.
# This should be combined with an internal read ahead style buffer that
Cassandra manages, similar to a BufferedInputStream but with our own machinery.
This buffer should read fairly large blocks of data off disk at at time. EBS,
for example, allows 1 IOP to be up to 256KB. A considerable amount of time is
spent in blocking I/O during compaction, reducing the frequency we read from
disk should speed up all sequential I/O operations.
> Improve disk access patterns during compaction compaction
> ---------------------------------------------------------
>
> Key: CASSANDRA-15452
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15452
> Project: Cassandra
> Issue Type: Improvement
> Components: Legacy/Local Write-Read Paths, Local/Compaction
> Reporter: Jon Haddad
> Priority: Normal
>
> On read heavy workloads Cassandra performs much better when using a low read
> ahead setting. In my tests I've seen an 5x improvement in throughput and
> more than a 50% reduction in latency. However, I've also observed that it
> can have a negative impact on compaction and streaming throughput. It
> especially negatively impacts cloud environments where small reads incur high
> costs in IOPS due to tiny requests.
> # We should investigate using POSIX_FADV_DONTNEED on files we're compacting
> to see if we can improve performance and reduce page faults.
> # This should be combined with an internal read ahead style buffer that
> Cassandra manages, similar to a BufferedInputStream but with our own
> machinery. This buffer should read fairly large blocks of data off disk at
> at time. EBS, for example, allows 1 IOP to be up to 256KB. A considerable
> amount of time is spent in blocking I/O during compaction, reducing the
> frequency we read from disk should speed up all sequential I/O operations.
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