ZFS does zfs send file system metadata flags as part of bio structure to disk drivers

Leo Prasath

New Member


Messages: 2

I want to know if FreeBSD / ZFS or UFS send a flag to lower level drivers regarding File System metadata in fashion similar to Linux where the ext3/4, jfs and other file systems use the
REQ_RW_META and BIO_RW_META flags in struct request and struct bio structures respectively to tell lower level block device driver about metadata I/O.

I really appreciate any help regarding this.
 

kpa

Beastie's Twin

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You need to clarify what those flags do on Linux. I would though guess no because the streams created deal only with dataset contents and replicating them on receiving side requires no special actions on the underlying providers.
 
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Leo Prasath

New Member


Messages: 2

this flag is set on those block I/O requests that the file system issues to file system metadata information like inodes, journal , block allocation bitmaps etc on the disk.

E.g. this thread here : http://lists.linuxfoundation.org/pipermail/containers/2009-April/017126.html says ext3 file system sets this flag on metadata i/o requests so that it is prioritized over data i/o requests in the I/O controller for the disk.

This thread tells how ext4 tags all journal i/o with the metadata flag : http://www.spinics.net/lists/linux-ext4/msg18213.html

This thread says XFS file system tags metadata I/O requests for better merging: http://oss.sgi.com/pipermail/xfs/2009-November/004631.html
 

kpa

Beastie's Twin

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Messages: 6,318

Uhm ok I read your question wrong and thought you are asking about zfs send/ zfs receive. Disregard my reply.
 
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