[Freeswitch-users] Performance bottleneck

Tue Aug 12 13:14:51 PDT 2008

Actually having evaluated MySQL for large scale environments it works well
up to a point... Postgres on the other hand has much more mature
replication, store procedures, triggers, a query cacher that insane and no
need to use mysql¹s so called Œhash tables¹ to get the data loaded into ram
(pg does this automagically via its caching mechanism)

Mix that with table partitioning and you have some fairly crazy numbers

Real world deployments doing some pretty complex LCR shows that a small
cluster (4 boxes) or old dell 2650s are able to sustain > 40K queries/sec
(~10% being inserts for CDRs)

When you get into this scale the real enterprise work that has been done on
pgsql starts to show thru... Companies like Greenplum feed a good bit of
their core performance tuning back to PgSQL... (for those that are wondering
pgsql is bsd licensed so its actually license compatible w/ FreeSwitch say
some someone want to look at replacing sqlite with a pgsql engine)

From: Darren Schreiber <d at d-man.org>
Reply-To: <freeswitch-users at lists.freeswitch.org>
Date: Tue, 12 Aug 2008 12:35:25 -0700
To: <freeswitch-users at lists.freeswitch.org>
Subject: Re: [Freeswitch-users] Performance bottleneck

I dont know if this makes any sense - it's just an idea.

If you're willing to take the hit of running MySQL, I know that it's
replication features could potentially be used. You can have the primary
MySQL server run in ramdisk and get all the performance benefits of doing so
while also writing log files to the ram disk in a seperate area. Those
logfiles can, using MySQL's built in replication features, be copied over to
a backup server and played backup, giving you both a hot spare as well as a
disk based backup.

This does three things for you:
1) Gives you backup on disk, while preserving performance in RAM
2) Gives you a live backup that you can quickly shunt things over to if for
some reason the primary dies
3) Allows you to handle spikes in volume. MySQL by default will just write
to the log files and they can be played back later by the (slower) backup
server, so a spike in volume of calls should not cause the server to slow
down per say. There is a small risk your data will be lost if there is a
failure for whatever is not copied over to the (slower) backup server, but
that's unlikely to be that huge a lag (better then nothing).

As to whether any of this applies (like why the heck you'd install MySQL on
a ramdisk to start), I can't say. but it's a thought...Oh, and you need a
lot of RAM ;-)

From: Ken Rice [mailto:krice at suspicious.org]
Sent: Tuesday, August 12, 2008 11:44 AM
To: freeswitch-users at lists.freeswitch.org
Subject: Re: [Freeswitch-users] Performance bottleneck

Actually I don¹t know of any mechanism that will back up the DB... Where
sqlite does work well for small to medium installations it only scales to a
point... Sqlite does not reuse Œnodes¹ in the db on an update... It marks
them as dead and creates a new entry... While this works ok on smaller
tables w/ light to medium updates after a while you have to compress or
vacuum the tables... This requires a table level lock with sqlite... FS does
have some things built in to handle this, but under load this can cause the
switch to appear to hang.

Switching over to use something like Postgresql (my prefered db) helps out a
good bit here, but keep in mind that in doing so you greatly increase the
resources required for the db. Also don¹t forget that pgsql has a similar
mechanism on how it handles updates, just don¹t forget to enable
auto-vacuuming on pgsql...  That is a discussion for a different list tho

K

From: Brian West <brian at freeswitch.org>
Reply-To: <freeswitch-users at lists.freeswitch.org>
Date: Tue, 12 Aug 2008 13:24:40 -0500
To: <freeswitch-users at lists.freeswitch.org>
Subject: Re: [Freeswitch-users] Performance bottleneck

Well putting the db in ram does help a bit but it has to keep states of
everything going on and do extra work for that... its a heavy task in
itself.

On Aug 12, 2008, at 1:19 PM, Michael Collins wrote:

> That begs the questionŠ is there a mechanism in sqlite  or Linux that allows
> for the RAM drive to be backed up periodically?   That would be a cool feature
> to get documented for those power users  like Ken! ;)
>  
> -MC
>  

Brian West
sip:brian at freeswitch.org

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