Switching of backends

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Switching of backends

Germain Maurice
Hi everybody,

I assume this question was already discussed but i didn't find the answer.

In a production environment, we plan to use Riak with Innostore and
after Bitcask has been approved for a production environment, we will
switch to it. So, we wonder if we can, only in the migration time,
switch off a node, change its backend,
and switch it on. This could work ?

I think the other way to do that is to backup the node, change the
backend, and restore the node. Do you agree with that ?

Thank you.

--
Germain Maurice
Administrateur Système/Réseau
Tel : +33.(0)1.42.43.54.33

http://www.linkfluence.net


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Re: Switching of backends

Sean Cribbs-2
Germain,

Yes, you could do that, but you would need to force read-repair to repopulate the node.  Doing so would be nearly as expensive as simply reloading the data from the backup.

Sean Cribbs <[hidden email]>
Developer Advocate
Basho Technologies, Inc.
http://basho.com/

On Jun 8, 2010, at 4:47 AM, Germain Maurice wrote:

> Hi everybody,
>
> I assume this question was already discussed but i didn't find the answer.
>
> In a production environment, we plan to use Riak with Innostore and after Bitcask has been approved for a production environment, we will switch to it. So, we wonder if we can, only in the migration time, switch off a node, change its backend,
> and switch it on. This could work ?
>
> I think the other way to do that is to backup the node, change the backend, and restore the node. Do you agree with that ?
>
> Thank you.
>
> --
> Germain Maurice
> Administrateur Système/Réseau
> Tel : +33.(0)1.42.43.54.33
>
> http://www.linkfluence.net
>
>
> _______________________________________________
> riak-users mailing list
> [hidden email]
> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com


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Re: Switching of backends

Germain Maurice
Sean,

Ok for the read-repair, I understand.
However, if i have to restore a node, what about datas written to the
cluster during the restore ?
Are they kept in "buffered" state while waiting the end of the restoring
phase ?
Do i have to force read-repair to complete the datas on the node ?

Regards,
Germain

Le 08/06/10 12:57, Sean Cribbs a écrit :

> Germain,
>
> Yes, you could do that, but you would need to force read-repair to repopulate the node.  Doing so would be nearly as expensive as simply reloading the data from the backup.
>
> Sean Cribbs<[hidden email]>
> Developer Advocate
> Basho Technologies, Inc.
> http://basho.com/
>
> On Jun 8, 2010, at 4:47 AM, Germain Maurice wrote:
>
>    
>> Hi everybody,
>>
>> I assume this question was already discussed but i didn't find the answer.
>>
>> In a production environment, we plan to use Riak with Innostore and after Bitcask has been approved for a production environment, we will switch to it. So, we wonder if we can, only in the migration time, switch off a node, change its backend,
>> and switch it on. This could work ?
>>
>> I think the other way to do that is to backup the node, change the backend, and restore the node. Do you agree with that ?
>>
>> Thank you.
>>
>> --
>> Germain Maurice
>> Administrateur Système/Réseau
>> Tel : +33.(0)1.42.43.54.33
>>
>> http://www.linkfluence.net
>>
>>
>> _______________________________________________
>> riak-users mailing list
>> [hidden email]
>> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
>>      
>    


--
Germain Maurice
Administrateur Système/Réseau
Tel : +33.(0)1.42.43.54.33

http://www.linkfluence.net


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Re: Switching of backends

Justin Sheehy
Germain,

If you have enough excess capacity that your cluster will be safe with
one less machine for a little while, you can do this another way.

Just "riak-admin leave" one machine, wait for it to hand off all of
its data, "riak stop", set up that machine with a new
install/config-file/backend/etc, and then start and join it as though
it was a brand new node.  Wait for it to get its share of data sent to
it in its new role, then repeat this process on the next node.

-Justin

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Re: Switching of backends

Mårten Gustafson
On 8 June 2010 14:25, Justin Sheehy <[hidden email]> wrote:
> If you have enough excess capacity that your cluster will be safe with
> one less machine for a little while, you can do this another way.
>
> Just "riak-admin leave" one machine, wait for it to hand off all of
> its data, "riak stop"

How would I know when a node has handed off all its data - would the
status command report that it doesn't own any partitions?



/m.

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Re: Switching of backends

Justin Sheehy
On Tue, Jun 8, 2010 at 8:29 AM, Mårten Gustafson
<[hidden email]> wrote:

> How would I know when a node has handed off all its data - would the
> status command report that it doesn't own any partitions?

Good question.  That won't quite do it, because the node will give up
ownership of the partitions first, and that will cause it to begin
pushing off that data to the new owners.

We hope to add a more obvious sign in the stats resource for this, but
for now the easiest way to tell is to just look at the disk usage in
the exiting node's data directory.  It should become empty when the
node completes handing off data.

-Justin

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Re: Switching of backends

Mårten Gustafson
On 8 June 2010 14:36, Justin Sheehy <[hidden email]> wrote:

>
> On Tue, Jun 8, 2010 at 8:29 AM, Mårten Gustafson
> <[hidden email]> wrote:
>> How would I know when a node has handed off all its data - would the
>> status command report that it doesn't own any partitions?
>
> Good question.  That won't quite do it, because the node will give up
> ownership of the partitions first, and that will cause it to begin
> pushing off that data to the new owners.
>
> We hope to add a more obvious sign in the stats resource for this, but
> for now the easiest way to tell is to just look at the disk usage in
> the exiting node's data directory.  It should become empty when the
> node completes handing off data.

"become empty" - does that hold for all different backends? I could
imagine the dets backend removing all files when it's done, but will
the InnoDB backend do the same?



/m

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