On Thu, Jul 9, 2020 at 10:33 AM Marc Roos <M.Roos@f1-outsourcing.eu> wrote:

What about ntfs? You have there a not quick option. Maybe it writes to the whole disk some random pattern. Why do you ask?

I am writing an API layer to plug into our platform, so I want to know if the format times can be deterministic or unbounded. From what I saw with ext3, ext4 and xfs volumes, the format time is actually not dependent on the size of the volume, so I just wanted to confirm if we can assume that, or if I am missing something. Thanks, Shridhar

-----Original Message----- Cc: ceph-users Subject: [ceph-users] Re: RBD thin provisioning and time to format a volume

Thanks Jason.

Do you mean to say some filesystems will initialize the entire disk during format? Does that mean we will see the entire size of the volume getting allocated during formatting? Or do you mean to say, some filesystem formatting just takes longer than others, as it does more initialization?

I am just trying to understand if there are cases where Ceph will allocate all the blocks for a filesystem during formation operations, OR if they continue to be thin provisioned (allocate as you go based on real data). So far I have tried with ext3, ext4 and xfs and none of them dont allocate all the blocks during format.

-Shridhar

On Thu, 9 Jul 2020 at 06:58, Jason Dillaman <jdillama@redhat.com> wrote:

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On Thu, Jul 9, 2020 at 12:02 AM Void Star Nill <void.star.nill@gmail.com> wrote:

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On Wed, Jul 8, 2020 at 4:56 PM Jason Dillaman <jdillama@redhat.com>

wrote:

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On Wed, Jul 8, 2020 at 3:28 PM Void Star Nill <void.star.nill@gmail.com>

wrote:

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Hello,

My understanding is that the time to format an RBD volume is not

dependent

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on its size as the RBD volumes are thin provisioned. Is this correct?

For example, formatting a 1G volume should take almost the same time as formatting a 1TB volume - although accounting for differences in latencies due to load on the Ceph cluster. Is that a fair assumption?

Yes, that is a fair comparison when creating the RBD image. However, a format operation might initialize and discard extents on

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the disk, so a larger disk will take longer to format.

Thanks for the response Jason. Could you please explain a bit more on the the format operation?

I'm not sure what else there is to explain. When you create a file system on top of any block device, it needs to initialize the block device. Depending on the file system, it might take more time for larger block devices because it's doing more work.

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Is there a relative time that we can determine based on the volume size?

Thanks Shridhar

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Thanks, Shridhar _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send

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-- Jason

-- Jason

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