samueldlightfoot commented on code in PR #4178:
URL: https://github.com/apache/cassandra/pull/4178#discussion_r2658933351
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src/java/org/apache/cassandra/io/sstable/format/SSTableReader.java:
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@@ -472,6 +475,9 @@ protected SSTableReader(Builder<?, ?> builder, Owner owner)
this.sstableMetadata = builder.getStatsMetadata();
this.header = builder.getSerializationHeader();
this.dfile = builder.getDataFile();
+ this.directIOSupported = FileUtils.isDirectIOSupported(dfile.file())
Review Comment:
On digging a little deeper, it's various flavours of filesystems such as
virtual/in-memory and network which can either throw or return zero values.
1. Virtual/In-Memory Filesystems: According to
https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/nio/file/FileStore.html,
the default implementation can throw UnsupportedOperationException
for non-local storage devices. Some virtual filesystems (like
https://github.com/google/jimfs/issues/183) may not properly implement
getBlockSize().
2. POSIX Specification: Per the
https://man7.org/linux/man-pages/man3/statvfs.3.html, "It is unspecified
whether all members of the returned struct have meaningful values on all file
systems."
3. Network Filesystems: NFS and other network filesystems may return
unreliable or zero values for block size in certain conditions, as
https://access.redhat.com/solutions/18357.
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