What is the layout of cephfs files?

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The layout xattrs of regular files is called ceph.file.layout, and the layout xattrs of directories is called ceph.dir.layout.

Layout field:

Pool

String, either ID or first name can be specified. It is the RADOS storage pool where the data object of the file resides.

Stripe_unit

Number of bytes, integers. The data blocks of a file are distributed according to this size (bytes) like RAID 0. All stripe units in a file are of the same size, and the last stripe unit is usually incomplete-that is, it contains the data at the end of the file and the unused "space" between the end of the data and the size of the fixed stripe unit.

Stripe_count

Round number. The number of consecutive stripe units that make up the RAID 0 stripe data.

Object_size

Integer bytes. File data is divided into RADOS objects according to this size

Use getfattr to read out the file layout:

Getfattr-n ceph.file.layout filename

Query a single file layout field:

Getfattr-n ceph.file.layout.pool filename

Getfattr-n ceph.file.layout.stripe_unit filename

Getfattr-n ceph.file.layout.stripe_count filename

Getfattr-n ceph.file.layout.object_size filename

Use setfattr to modify the file layout:

Setfattr-n ceph.file.layout.pool-v pool_num file_name-set pool id

Setfattr-n ceph.file.layout.stripe_unit-v 1048576 filename-- sets the stripe size

Setfattr-n ceph.file.layout.stripe_count-v 2 filename-- sets the number of stripes across

Setfattr-n ceph.file.layout.object_size-v 1048576 filename-- sets the object size

Query directory particularity:

Use getfattr to read out the directory layout:

Getfattr-n ceph.dir.layout.pool dirname

Use setfattr to modify the directory layout:

Setfattr-n ceph.dir.layout.pool-v pool_num file_name-set pool id

Setfattr-n ceph.dir.layout.stripe_unit-v 1048576 filename-- sets the stripe size

Setfattr-n ceph.dir.layout.stripe_count-v 2 filename-- sets the number of stripes across

Setfattr-n ceph.dir.layout.object_size-v 1048576 filename-- sets the object size

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