SUM and Group By Optimization
Would i benefit in this case from the myisam table engine?


No you won't.


  What could i do to further optimize the query or the settings?


Materialize the query.

MySQL does not have built-in means to do that easily (similar to indexed views in SQL Server or materialized views in Oracle) so you'll have to put some effort into it.

Create a table like this:

CREATE TABLE log_customer_date
        (
        customer BIGINT NOT NULL,
        logdate DATE NOT NULL,
        sumbytes BIGINT NOT NULL,
        countrecords BIGINT NOT NULL,
        PRIMARY KEY (customer, logdate)
        )


fill it:

INSERT
INTO    log_customer_date
SELECT  customer, logdate, SUM(bytes) sumbytes, COUNT(*) countrecords
FROM    logdata
GROUP BY
        customer, logdate


and add further records in a trigger:

INSERT
INTO    log_customer_date
VALUES  (NEW.customer, NEW.logdate, NEW.bytes, 1)
ON DUPLICATE KEY
UPDATE  sumbytes = sumbytes + VALUES(sumbytes),
        countrecords = countrecords + VALUES(countrecords)


or in a script every once in a while:

INSERT
INTO    log_customer_date
SELECT  customer, logdate, SUM(bytes) sumbytes, COUNT(*) countrecords
FROM    logdata
WHERE   id &gt; :lastid
GROUP BY
        customer, logdate
ON DUPLICATE KEY
UPDATE  sumbytes = sumbytes + VALUES(sumbytes),
        countrecords = countrecords + VALUES(countrecords)


, recording the highest id by the moment of the insert somewhere.