dhis2-devs team mailing list archive

[Calle Hedberg <calle.hedberg@xxxxxxxxx>]

Hi,

One (presumably) simple solution is to stagger analytics on a year by year
basis - i.e. run and complete 2009 before processing 2010. That would
reduce temp disk space requirements significantly while (presumably) not
changing the general design.

Regards
Calle

On 26 July 2016 at 10:24, Jason Pickering <jason.p.pickering@xxxxxxxxx>
wrote:

> Hi Devs,
> I am seeking some advice on how to try and decrease the amount of disk
> usage with DHIS2.
>
> Here is a list of the biggest tables in the system.
>
>  public.datavalue                                   | 2316 MB
>  public.datavalue_pkey                         | 1230 MB
>  public.in_datavalue_lastupdated          | 680 MB
>
>
> There are a lot more tables, and all in all, the database occupies about
> 5.4 GB without analytics.
>
> This represents about 30 million data rows, so not that big of a database
> really. This server is being run off of a Digital Ocean virtual server with
> 60 GB of disk space. The only thing on the server really is Linux,
> Postgresql and Tomcat. Nothing else. With out analytics and everything
> installed for the system, we have about 23% of that 60 GB free.
>
> When analytics runs, it maintains a copy of the main analytics tables (
> analytics_XXXX) and creates temp tables like analytics_temp_2004. When
> things are finished and the indexes are built, the tables are swapped. This
> ensures that analytics resources are available while analytics are being
> built, but the downside of this is that A LOT more disk space is required,
> as now we effectively have two copies of the tables along with all their
> indexes, which are quite large themselves (up to 60% the size of the table
> itself).  Here's what happens when analytics is run
>
>  public.analytics_temp_2015              | 1017 MB
>  public.analytics_temp_2014              | 985 MB
>  public.analytics_temp_2011              | 952 MB
>  public.analytics_temp_2010              | 918 MB
>  public.analytics_temp_2013              | 885 MB
>  public.analytics_temp_2012              | 835 MB
>  public.analytics_temp_2009              | 804 MB
>
> Now each analytics table is taking about 1 GB of space. In the end, it
> adds up to more than 60 GB and analytics fails to complete.
>
> So, while I understand the need for this functionality, I am wondering if
> we need a system option to allow the analytics tables to be dropped prior
> to regenerating them, or to have more control over the order in which they
> are generated (for instance to generate specific periods). I realize this
> can be done from the API or the scheduler, but only for the past three
> relative years.
>
>  The reason I am asking for this is because its a bit of a pain (at the
> moment) when using Digital Ocean as a service provider, since their stock
> disk storage is 60 GB. With other VPS providers (Amazon, Linode), its a bit
> easier, but DigitalOcean only supports block storage in two regions at the
> moment. Regardless, it would seem somewhat wasteful to have to have such a
> large amount of disk space, for such a relatively small database.
>
> Is this something we just need to plan for and maybe provide better
> documentation on, or should we think about trying to offer better
> functionality for people running smaller servers?
>
> Regards,
> Jason
>
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Calle Hedberg

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