Set object mtime

Set object mtime

[Damien Churchill]

Does anyone know if it's possible to set an objects mtime at all in RADOS?

Regards,
Damien

Re: Set object mtime

[Wido den Hollander]

On 03/25/2013 12:27 PM, Damien Churchill wrote:
> Does anyone know if it's possible to set an objects mtime at all in RADOS?
>

You mean with a specific operation while not modifying the content of 
the object?

I checked the rados API, but I couldn't find any method which allows you 
to do so.

Wido

> Regards,
> Damien
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-- 
Wido den Hollander
42on B.V.

Phone: +31 (0)20 700 9902
Skype: contact42on

Re: Set object mtime

[Damien Churchill]

On 25 March 2013 19:18, Wido den Hollander <wido@42on.com> wrote:
> On 03/25/2013 12:27 PM, Damien Churchill wrote:
>>
>> Does anyone know if it's possible to set an objects mtime at all in RADOS?
>>
>
> You mean with a specific operation while not modifying the content of the
> object?
>
> I checked the rados API, but I couldn't find any method which allows you to
> do so.

Neither could I. I guess the question should be changed to:

How difficult would it be to allow the modification time to be set
(including setting it to a time in the past) without changing the
object?

>
> Wido
>
>> Regards,
>> Damien
>> --
>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
>
> --
> Wido den Hollander
> 42on B.V.
>
> Phone: +31 (0)20 700 9902
> Skype: contact42on

Re: Set object mtime

[Sage Weil]

On Mon, 25 Mar 2013, Damien Churchill wrote:
> On 25 March 2013 19:18, Wido den Hollander <wido@42on.com> wrote:
> > On 03/25/2013 12:27 PM, Damien Churchill wrote:
> >>
> >> Does anyone know if it's possible to set an objects mtime at all in RADOS?
> >>
> >
> > You mean with a specific operation while not modifying the content of the
> > object?
> >
> > I checked the rados API, but I couldn't find any method which allows you to
> > do so.
> 
> Neither could I. I guess the question should be changed to:
> 
> How difficult would it be to allow the modification time to be set
> (including setting it to a time in the past) without changing the
> object?

The CREATE operation just creates the object if it doesn't exist.  You can 
use that op and set the mtime to whatever you want.  You probably need to 
use the C++ bindings with the ObjectWriteOperation method; I don't think 
there is a standalone call for it (tho one is easily added).

sage

Re: Set object mtime

[Damien Churchill]

On 25 March 2013 19:38, Sage Weil <sage@inktank.com> wrote:
> On Mon, 25 Mar 2013, Damien Churchill wrote:
>> On 25 March 2013 19:18, Wido den Hollander <wido@42on.com> wrote:
>> > On 03/25/2013 12:27 PM, Damien Churchill wrote:
>> >>
>> >> Does anyone know if it's possible to set an objects mtime at all in RADOS?
>> >>
>> >
>> > You mean with a specific operation while not modifying the content of the
>> > object?
>> >
>> > I checked the rados API, but I couldn't find any method which allows you to
>> > do so.
>>
>> Neither could I. I guess the question should be changed to:
>>
>> How difficult would it be to allow the modification time to be set
>> (including setting it to a time in the past) without changing the
>> object?
>
> The CREATE operation just creates the object if it doesn't exist.  You can
> use that op and set the mtime to whatever you want.  You probably need to
> use the C++ bindings with the ObjectWriteOperation method; I don't think
> there is a standalone call for it (tho one is easily added).
>

Okay thanks! A call in the C API would be handy. I was wanting to look
at creating a tool to sync RADOS between clusters. Is that anything
that's in the development plan already? I noticed the email about the
rbd-diff tool yesterday.

Re: Set object mtime

[Sylvain Munaut]

Hi,

> Okay thanks! A call in the C API would be handy. I was wanting to look
> at creating a tool to sync RADOS between clusters. Is that anything
> that's in the development plan already?

I was just thinking of the same thing.

Basically I want rsync between pools, mostly to allow changing the
number of PG with minimum down time. The current method is to copy the
pool but that implies nothing is writing to it in the mean time and I
can't shutdown operations for that long.

Did you end up writing that tool ?


Cheers,

    Sylvain

Re: Set object mtime

[Gregory Farnum]

On Thu, Jul 11, 2013 at 6:56 AM, Sylvain Munaut
<s.munaut@whatever-company.com> wrote:
> Hi,
>
>> Okay thanks! A call in the C API would be handy. I was wanting to look
>> at creating a tool to sync RADOS between clusters. Is that anything
>> that's in the development plan already?
>
> I was just thinking of the same thing.
>
> Basically I want rsync between pools, mostly to allow changing the
> number of PG with minimum down time. The current method is to copy the
> pool but that implies nothing is writing to it in the mean time and I
> can't shutdown operations for that long.
>
> Did you end up writing that tool ?

Why do you want to copy the data to change the PG count? PG splitting
is supported now, so unless you need to do merging for some reason you
should be good to go. :)
-Greg
Software Engineer #42 @ http://inktank.com | http://ceph.com

Re: Set object mtime

[Sylvain Munaut]

Hi,

> Why do you want to copy the data to change the PG count? PG splitting
> is supported now, so unless you need to do merging for some reason you
> should be good to go. :)

I need to do merging :)

At the time the PG count formula wasn't too clear and I got too many
PGs which tend to slow things down, slow down peering and things like
that. Also non-power of two seem to have less favorable data
distributions.

It also seems to be the only way to enable that flag to hash the pool
id at the moment.

Cheers,

    Sylvain