Re: [ceph-commit] Ceph Zfs

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On 10/25/2012 09:46 PM, Raghunandhan wrote:
Hi Sage,

Thanks for replying back, Once a zpool is created if i mount it on
/var/lib/ceph/osd/ceph-0 the cephfs doesnt recognize it as a superblock
and hence it fails,

I assume you mean "once a zfs is created"?  One can't mount zpools, can one?

Im trying to build this on our cloud storage since
btrfs has not been stable nor they have come up with online dedup i have
no other choice for now to work with zfs ceph which makes sense.

So what i exactly did was created a zpool store
1 Then used the same store and made a block device from it using zfs create
2 Once the zfs create was successful i was able to format with ext4
using xattr
3 On top of it was the ceph

Following this process doesnt make sense because of multiple layer on
the storage and the ceph consumes a lot of RAM and cpu cycles which ends
up in kernel hung task. It would be great if there is a way i could
directly use the zfs pool with ceph and make it work.

Have you actually tried making a zfs filesystem in the zpool, and using that as backing store for the osd?


---
Regards,
Raghunandhan.G
IIHT Cloud Solutions Pvt. Ltd.
#15, 4th Floor, 'A' Wing, Sri Lakshmi Complex,
St. Marks Road, Bangalore - 560 001, India

On 25-10-2012 22:06, Sage Weil wrote:
[moved to ceph-devel]

On Thu, 25 Oct 2012, Raghunandhan wrote:
Hi All,

I have been working around ceph quite a long and trying to stitch zfs
with
ceph. I was able to do it to certain extent as follows:
1. zpool creation
2. set dedup
3. create a mountable volume of zfs (zfs create)
4. format the volume with ext4 and enabling xattr
5. mkcephfs on the volume

This actually works and dedup is perfect. But i need to avoid
multiple layers
on the storage since the performance is very slow and the kernel timeout
occurs often for a 8GB RAM. I want to test the performance between
btrfs and
zfs. I want to avoid the above multiple layering on storage and make
the ceph
cluster aware of zfs. Let me know if anyone has workaround this.

I'm not familiar enough with zfs to know what 'mountable volume' means..
is that a block device/lun that you're putting ext4 on?  Probably the
best
results will come from creating a zfs *file system* (using the ZPL or
whatever it is) and running ceph-osd on top of that.

There is at least one open bug from someone having problems there, but
we'd very much like to sort out the problem.

sage

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