[DRBD-user] Secondary node saturises RAID array

Matteo Tescione matteo at rmnet.it
Tue Apr 15 18:24:22 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


> Hi,
> 
>> Thanks, and I'll report my findings back to this list.
> 
> The problem wasn't caused by the RAID-6 setup. On two RAID-10 arrays the
> problem persisted. The sync system calls still take quite long. Write
> performance was actually a bit lower, but nothing to be worried about.

Have you tried usin external metadata?
I'm going to place the metadata over a i-raid 4gb ddr RAM drive to speed up
those sync operations. Am i alone here?

However can't realize why your write performance becomes lower using raid10
setup. How many spindle? Give us a more detailed idea of your setup.
Cheers,
--
matteo
> 
> MySQL commit performance gains of almost 1500% were achievable by using the
> following MySQL parameter: innodb_flush_log_at_trx_commit = 2. It simply
> limits the amount of calls to sync() to once a second.
> 
> Of course this isn't an ideal situation, but it's good enough to hit
> production. If anyone has an idea about how to speed up sync(), that'll be
> really helpful, still.
> 
> Thanks for all the help sofar.





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