On Tue, 12 Mar 2013, Varun Chandramouli wrote:
> Hi All,
> I was running some experiments on my 3-node ceph cluster (mounted at
> /mnt/ceph), and noticed unexpected behavior regarding cephfs set_layout
> command.
>
> root@varunc-virtual-machine:/mnt/ceph/folder1# touch test3
> root@varunc-virtual-machine:/mnt/ceph/folder1# cephfs test3 set_layout -p 3
> -s 41943040
> root@varunc-virtual-machine:/mnt/ceph/folder1# cephfs test3 show_layout
> layout.data_pool: 3
> layout.object_size: 41943040
> layout.stripe_unit: 4194304
> layout.stripe_count: 1
> root@varunc-virtual-machine:/mnt/ceph/folder1# vi test3
> root@varunc-virtual-machine:/mnt/ceph/folder1# cephfs test3 show_layout
> layout.data_pool: 0
> layout.object_size: 4194304
> layout.stripe_unit: 4194304
> layout.stripe_count: 1
>
> I create an empty file and set its layout (which it displays correctly in
> the corresponding show_layout). Then, I open the file and write something to
> it (a single line of text), and again use the show_layout command, and it
> reverts to the default layout. What is the reason for this? Is it that I can
> not write to the file simply using vi editor? Because when I do the same
> process again, but instead use cat command to redirect the input into the
> new file, the layout set by me persists.
I think this is because vi is doing something like:
vi foo:
copy foo to foo.swp
...edit foo.swp...
on save, rename foo.swp to foo
which means it's basically a different file. You can verify this by
looking at the ino field from 'stat test3' before and after editing with
vi.
> root@varunc-virtual-machine:/mnt/ceph/folder1# touch test4
> root@varunc-virtual-machine:/mnt/ceph/folder1# cephfs test4 set_layout -p 3
> -s 41943040
> root@varunc-virtual-machine:/mnt/ceph/folder1# cephfs test4 show_layout
> layout.data_pool: 3
> layout.object_size: 41943040
> layout.stripe_unit: 4194304
> layout.stripe_count: 1
> root@varunc-virtual-machine:/mnt/ceph/folder1# cat file1.txt > test4
> root@varunc-virtual-machine:/mnt/ceph/folder1# cephfs test4 show_layout
> layout.data_pool: 3
> layout.object_size: 41943040
> layout.stripe_unit: 4194304
> layout.stripe_count: 1
>
> Also, how do I set the layout for an entire directory. I tried the
> following:
> root@varunc-virtual-machine:/mnt/ceph# cephfs folder2/ set_layout -p 3 -s
> 4194304
> Error setting layout: Invalid argument
> root@varunc-virtual-machine:/mnt/ceph# cephfs folder1/ set_layout -p 0 -s
> 4194304
> Error setting layout: Invalid argument
>
> (folder1 contains around 1000 files, folder2 is empty)
Can you try using the virtual xattr interface instead?
getfattr -d -m - mydir
setfattr -n ceph.dir.layout.pool -v mypool mydir
...
sage
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