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From Stefano Ortolani <ostef...@gmail.com>
Subject Re: [Marketing Mail] Migrating to incremental repairs
Date Thu, 19 Nov 2015 11:13:02 GMT
As far as I know, docs is quite inconsistent on the matter.
Based on some research here and on IRC, recent versions of Cassandra do no
require anything specific when migrating to incremental repairs but the the
-inc switch even on LCS.

Any confirmation on the matter is more than welcome.

Regards,
Stefano

On Wed, Nov 18, 2015 at 3:59 PM, Reynald Bourtembourg <
reynald.bourtembourg@esrf.fr> wrote:

> Well,
>
> By re-reading my e-mail, I understood the rationale behind doing a full
> sequential repair for each node.
> I was confused by the fact that in our case, we have 3 nodes with RF = 3,
> so all the nodes are storing all replicas.
> So we are in a special case.
> As soon as you have more than 3 nodes, this is no longer the case.
>
> In any case, in our special case (3 nodes and RF=3), could we apply the
> following migration procedure?:
> - disableautocompaction on all nodes at the same time
>  - run the full sequential repair
>  - For each node:
>         - stop the node
>         - Use the tool sstablerepairedset to mark all the SSTables that
> were created before you disabled compaction.
>         - Restart Cassandra
>
> I'd be glad if someone could answer to my other questions in any case ;-).
>
> Thanks in advance for your help
>
> Reynald
>
>
>
> On 18/11/2015 16:45, Reynald Bourtembourg wrote:
>
> Hi,
>
> We currently have a 3 nodes Cassandra cluster with RF = 3.
> We are using Cassandra 2.1.7.
>
> We would like to start using incremental repairs.
> We have some tables using LCS compaction strategy and some others using
> STCS.
>
> Here is the procedure written in the documentation:
>
> To migrate to incremental repair, one node at a time:
>
>    1. Disable compaction on the node using nodetool disableautocompaction.
>    2. Run the default full, sequential repair.
>    3. Stop the node.
>    4. Use the tool sstablerepairedset to mark all the SSTables that were
>    created before you disabled compaction.
>    5. Restart cassandra
>
>
> In our case, a full sequential repair takes about 5 days.
> If I follow the procedure described above and if my understanding is
> correct, it's gonna take at least 15 days (3 repairs of 5 days) before to
> be able to use the incremental repairs, right(?), since we need to do it
> one node at a time (one full sequential repair per node?).
>
> If my understanding is correct, what is the rationale behind the fact that
> we need to run a full sequential repair once for each node?
> I understood a full sequential repair would repair all the sstables on all
> the nodes. So doing it only once should be enough, right?
>
> Is it possible to do the following instead of what is written in the
> documentation?:
>  - disableautocompaction on all nodes at the same time
>  - run the full sequential repair
>  - For each node:
>         - stop one node
>         - Use the tool sstablerepairedset to mark all the SSTables that
> were created before you disabled compaction.
>         - Restart Cassandra
> Without having to run the full sequential repair 3 times?
>
> The documentation states that if we don't execute this migration
> procedure, the first time we will run incremental repair, Cassandra will
> perform size-tiering on all SSTables because the repair/unrepaired status
> is unknown and this operation can take a long time.
> Do you think this operation could take more than 15 days in our case?
>
> I understood that we only need to use sstablerepairedset on the SSTables
> related to the tables using LCS compaction strategy and which were created
> before the auto compaction was disabled.
> Is my understanding correct?
>
> The documentation is not very explicit but I suppose the following
> sentence:
> "4. Use the tool sstablerepairedset to mark all the SSTables that were
> created before you disabled compaction."
> means we need to invoke "sstablerepairedset --is-repaired -f
> list_of_sstable_names.txt" on the LCS SSTables that were created before the
> compaction was disabled.
>
> Is this correct?
>
> Do we need to enableautocompaction again after the Cassandra restart or is
> it done automatically?
>
> Would you recommend us to upgrade our Cassandra version before starting
> the incremental repair migration?
>
> Thank you for your help and sorry for the long e-mail.
>
> Reynald
>
>
>
>
>
>
>

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