SQL on ?

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Self-answering:

BEWARE! :-/

I tried and installed mysql on the Pi (modell B). After converting the

everything worked well. It seemed.

But then I tried to sync approx. 400 vcards via carddav ? load increased to 12, peaked at 20 (!) and even my 100 MB swap ran full (this never, never happened before in one year). And? Well, owncloud could not manage it, it seems. The second computer synced and got nearly 600 vcards, but looots of doublettes. And I could not reach the adressbook via https.

So, sad but true, it seems the Pi won?t be able to handle this combination. Bad due to sqlite is too slow and blocks with locks. With mysql this did not happen, but the machine maybe had not enough power? I run it with 800 MHz scaling governor.

Such a pitty.

B. Alabay

In article ,

Did you tune the MySQL engine to use less RAM? If you do, then it won't swap and should be much more responsive.

Gordon

No. I had questioned that here ? no-one told me something about tuning

unbelievable. But it was shocking how much mysql sucks the cpu.

Syncing big address books? No way.

B. Alabay

On Mon, 17 Nov 2014 11:24:47 +0000 (UTC), Ba?ar Alabay declaimed the following:

But which table type(s) had you defined? MyISAM, InnoDB, some other?

When doing such block updates, did you try disabling the index first, then letting it build the index after the update completed?

There are a LOT of configuration parameters for MySQL that maybe should be looked at...

In article ,

Make sure it's not swapping first. Really. That's important - if it swaps, then you'll lost 99% of any avalable anything )-:

Edit /etc/my.cnf and look for the numbers.

I've never installed Debians version of MySQL though - but the MySQL source distribution comes with small, medium and large standard configuration files - seeing if they exist might be a good starting point (ie. start with the small one)

Gordon

Well, the problem is, I just wanted owncloud to work. Not to dive deepest into mysql :-/

B. Alabay

Ehm, I just switched the database type from sqlite to mysql ? means, let owncloud convert and switch. So me, I hadn?t defined anything.

I just wanted owncloud to work. I?m not a database specialist. As with sqlite, one sets up and it goes. So the owncloud team itself just states mysql is the better way for bigger (what this means) installations. Nothing more. A bit poor information for the masses.

Maybe that?s the problem :-|

B. Alabay

In article ,

What do you think? It's the Pi. Or specifically Linux running on the Pi deciding that some program or other needs more memory, so it (Linux) swaps stuff out to disk (SD card)

It's not going to happen. Only the most trivial of mysql systems on a Pi is going to work without any sort of tuning. You "get away" with it these days because servers have stupid amount of memory and fast processors. A Pi has neither, so you'll need to tune.

There are gigabytes of manuals, documents, how-to's, etc. online about MySQL tuning. Start reading.

Gordon

On Mon, 17 Nov 2014 21:57:25 +0000 (UTC), Ba?ar Alabay declaimed the following:

It probably is working... But it's your initial build of the database that could be killing you.

Consider: once you loaded that database, how often do you expect to make changes to the data? How big are the changes?

Changing one record a day isn't going to be noticed. Retrieving the entire data content probably won't be noticed...

But bulk loading lots of records with active index files is going to result in lots of thrashing.

You'll have to examine what type of tables "owncloud" creates... MyISAM will have sets of:

xxx.frm xxx.MYD xxx.MYI {at least, the version I run on Win7 creates such}

.frm is the table schema, .MYD is the table data, and .MYI is the table index. xxx is the table name.

InnoDB mixes the tables into a "single" file -- but creates overflow files as needed.

Is MySQL Workbench available for the OS on the PI? Possibly not -- I know it runs on Win7 but that's as a prebuilt executable.

mysql-workbench is available, as is mysqltuner which may help decide which parameters to set.

I don't run MySQL on a Pi, but I do have several (admittedly not too busy) MySQL databases and an Apache server running on an old PC which has 384MB RAM and a 500MHz Celeron CPU. It's a bit faster than a Pi.

mysql, the pi never swapped for over a year.

I cannot experiment with this little machine. That?s the point. So I have to wait.

B. Alabay

You mean the filling up? Maybe.

Well, sometimes there are lots of changes in calendars and file syncs. All these reflect to the db I guess.

I even don?t know where the db itself is :-) Is it like with sqlite just inside /data (OC) or somewhere else?

Single file sounds like sqlite.

I haven?t to had to do anything with db issues for the last 20 years. Before that, yes, on Atari :-)

B. Alabay

Hm, as I run the pi without any GUI ? maybe I could have used these on OSX and connect to the pi. But for now I don?t have time and possibilities to experiment with that.

Maybe a bit better cooled, too.

B. Alabay

Maybe it would be reasonable to expect that a MySQL package distributed in a Pi distribution is already tuned not to use more memory than a Pi usually has available.

OTOH, I know someone who runs an out-of-the-box VoIP exchange install on a Pi (Asterisk plus some web config frontend that I think uses MySQL as configuration storage), so either the tuning is better on that install or it is not so much of an issue until you really start to load it.

mysqltuner is a command line utility. It's just a perl script that analyses the databases and gives a few suggestions and reports.

Probably needs to be. But the fan doesn't run very often. It's an old laptop.

The Pi doesn't need cooling.

The default location for the database files is /var/lib/mysql/$databasename/

I believe that's a single (.frm) file per table, not per DB like sqlite.

Well - the issue here is that Raspbian is essentially Debian re-compiled for the Pi and is fairly generic rather than being targetted.

What might be an idea is for some enterprising individual to create & release just the my.cfg configuration file tailored for the Pi. Any takers?

That particular asterisk is pretty light weight. Hardly anything is stored in the database.

My own asterisk based PBX runs in 128MB of RAM with no SQL (uses apache & php though)

Gordon

I would not have considered a db with 600 personal contacts a heavy load until I read here that it causes a problem.