Fwd: Query performance against table with/out backup

[Andrew Mashenkov]

Crossposting to dev.

Igniters,

For now we allow user to change number of backups in configuration between
grid restarts with no error.
An user see new configuration object from code, but see old in visor.

So, if user rise number of backups between grid restarts, it will be able
to start the grid successfully.
Seems, then user see more backups in cacheConfiguration then really Ignite
will have.

I slightly rework our persistence examples to check this case and it looks
to be a true.
I see new configuration on client and on servers, but backups=2 can't
prevent data loss in case of 2 nodes failed.

Steps to reproduce (I waited for awhile at each step for rebalance had been
finished).
1. Start grid with backups=1 and persistence enabled.
2. Fill with data and shutdown a grid.
3. Change config with backup=2.
4. Start grid and wait for awhile.
5. Kill 2 nodes and observe data loss.


[1] https://issues.apache.org/jira/browse/IGNITE-6781


---------- Forwarded message ----------
From: blackfield <[hidden email]>
Date: Thu, Oct 19, 2017 at 9:29 PM
Subject: Re: Query performance against table with/out backup
To: [hidden email]


Here, I am trying to ascertain that I set backup == 2 properly as I
mentioned
above that I do not see query performance difference between backup ==1 and
backup == 2.

I want to make sure that I configure my cache properly.

When I set the backup==2 (to have three copies), I notice the following via
visor.

The Affinity Backups is still equal to 1. Is this a different property than
number of backups? If it is not, how do one see the number of backups a
cache is configured for?

Invoking "cache -a" to see the detail cache stat, with backup==2, under the
size column, the sum of entries on all nodes is equal to the number of rows
in the table * 2.  It appears this is the case for backup >= 1?

As in, only one set of backup will be stored in off heap regardless the
number of backups are specified?




--
Sent from: http://apache-ignite-users.70518.x6.nabble.com/



--
Best regards,
Andrey V. Mashenkov

[dsetrakyan]

Andrey, thanks for pointing this out.

I think this is a serious usability issue. Do I understand correctly that
we currently simply ignore a change in backup count if the persistence is
enabled? If yes, we should fix it ASAP. I would also add a check for other
configuration properties, like the affinity function, cache name, etc...

D.

On Fri, Oct 27, 2017 at 7:46 AM, Andrey Mashenkov <
[hidden email]> wrote:

> Crossposting to dev.
>
> Igniters,
>
> For now we allow user to change number of backups in configuration between
> grid restarts with no error.
> An user see new configuration object from code, but see old in visor.
>
> So, if user rise number of backups between grid restarts, it will be able
> to start the grid successfully.
> Seems, then user see more backups in cacheConfiguration then really Ignite
> will have.
>
> I slightly rework our persistence examples to check this case and it looks
> to be a true.
> I see new configuration on client and on servers, but backups=2 can't
> prevent data loss in case of 2 nodes failed.
>
> Steps to reproduce (I waited for awhile at each step for rebalance had been
> finished).
> 1. Start grid with backups=1 and persistence enabled.
> 2. Fill with data and shutdown a grid.
> 3. Change config with backup=2.
> 4. Start grid and wait for awhile.
> 5. Kill 2 nodes and observe data loss.
>
>
> [1] https://issues.apache.org/jira/browse/IGNITE-6781
>
>
> ---------- Forwarded message ----------
> From: blackfield <[hidden email]>
> Date: Thu, Oct 19, 2017 at 9:29 PM
> Subject: Re: Query performance against table with/out backup
> To: [hidden email]
>
>
> Here, I am trying to ascertain that I set backup == 2 properly as I
> mentioned
> above that I do not see query performance difference between backup ==1 and
> backup == 2.
>
> I want to make sure that I configure my cache properly.
>
> When I set the backup==2 (to have three copies), I notice the following via
> visor.
>
> The Affinity Backups is still equal to 1. Is this a different property than
> number of backups? If it is not, how do one see the number of backups a
> cache is configured for?
>
> Invoking "cache -a" to see the detail cache stat, with backup==2, under the
> size column, the sum of entries on all nodes is equal to the number of rows
> in the table * 2.  It appears this is the case for backup >= 1?
>
> As in, only one set of backup will be stored in off heap regardless the
> number of backups are specified?
>
>
>
>
> --
> Sent from: http://apache-ignite-users.70518.x6.nabble.com/
>
>
>
> --
> Best regards,
> Andrey V. Mashenkov
>