Re: Sparse files copied to CephFS not sparse

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For cephfs, the size reported by 'ls -s' is the same as file size. see
http://ceph.com/docs/next/dev/differences-from-posix/

Regards
Yan, Zheng


On Mon, Sep 16, 2013 at 5:12 PM, Jens-Christian Fischer
<jens-christian.fischer@xxxxxxxxx> wrote:
>
> Hi all
>
> as part of moving our OpenStack VM instance store from dedicated disks on the physical hosts to a CephFS backed by an SSD pool, we noticed that the files created on CephFS aren't sparse, even though the original files were.
>
> This is on
> root@s2:~# ls -lhs /var/lib/nova/instances/_base
> total 63G
> 750M -rw-r--r-- 1 nova         nova 2.0G Jul 10 21:40 1a11de23fe75a210b4da631366513cb7c22ef311
> 750M -rw-r--r-- 1 libvirt-qemu kvm   10G Jul 10 21:40 1a11de23fe75a210b4da631366513cb7c22ef311_10
>
>
> vs
>
> root@s2:~# ls -lhs /mnt/instances/instances/_base/1a11de23fe75a210b4da631366513cb7c22ef311*
> 1.2G -rw-r--r-- 1 nova         nova 1.2G Sep  5 16:56 /mnt/instances/instances/_base/1a11de23fe75a210b4da631366513cb7c22ef311
>  10G -rw-r--r-- 1 libvirt-qemu kvm   10G Jul 10 21:40 /mnt/instances/instances/_base/1a11de23fe75a210b4da631366513cb7c22ef311_10
>
> We have used different ways of copying the files (tar and rsync) and specified the sparse options:
>
> # rsync -rtvupogS -h  /var/lib/nova/instances/ /mnt/instances/instances
> or
> # (cd /var/lib/nova/instances ; tar -Svcf - .)|(cd /mnt/instances/instances ; tar Sxpf -)
>
> The OSDs we use for this pool are backed by XFS (which has a problem with sparse files, unless one specifies allocation block size options in the mounts) http://serverfault.com/questions/406069/why-are-my-xfs-filesystems-suddenly-consuming-more-space-and-full-of-sparse-file, https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=055388a3188f56676c21e92962fc366ac8b5cb72. We have mounted the XFS partitions for the OSDs with this option, but I assume that this shouldn't impact the way CephFS handles sparse files.
>
> I seem to remember that the copying of sparse files worked a couple of months ago (ceph-fs kernel 3.5 on btrfs OSDs), but now we used Kernel 3.10 and recently ceph-fuse to mount the CephFS.
>
> Are we doing something wrong, or is this not supported by CephFS?
>
> cheers
> jc
>
>
>
>
>
> --
> SWITCH
> Jens-Christian Fischer, Peta Solutions
> Werdstrasse 2, P.O. Box, 8021 Zurich, Switzerland
> phone +41 44 268 15 15, direct +41 44 268 15 71
> jens-christian.fischer@xxxxxxxxx
> http://www.switch.ch
>
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>
>
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