On Wed, Dec 15, 2010 at 6:44 AM, Friso van Vollenhoven
<[email protected]> wrote:
> On the master UI HBase shows doing between 10K and 50K requests per second
> with quite some drops to almost zero for some amount of time, while without
> WAL for the same job it easily reaches over 100K sustained.
Those numbers are in line with my experience. Disabling the WAL gives
you a performance boost of about an order of magnitude. It's expected
because no WAL = memory accesses only vs. WAL = HDFS latency.
If your cluster is grinding to a halt past a certain point, you might
wanna take a look at the IO utilization on your boxes and maybe also
network utilization. How many disks per box do you have? What type
of disks are they? Have you looked at the output of "iostat -xkd 1"
while the cluster was performing poorly? Do you see a lot of iowait
("wa" column in "top")?
--
Benoit "tsuna" Sigoure
Software Engineer @ www.StumbleUpon.com
