Poor performance solved WAS: Re: [DRBD-user] 2.6.24-rc1 oops

Pierguido Lambri pierg75 at yahoo.it
Sun Nov 11 11:49:35 CET 2007

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

Matteo Tescione wrote:
> Leroy, drbd folks,
> After a while of collecting and profiling my systems i discovered that our
> poor performance problems were not related of processor, raid controller or
> kernel configuration.
> It's all about raid5/6 level configurations that is absolutely unreliable.
> In details reading and writing directly to the raid disk, with an ext3
> partition for example, gives more than 200 mbyte/sec with await and svc time
> of approx 1.2 ms versus reading and writing with drbd (either syncing or
> live i/o) gives extremely poor performance (i got 30-40 mbyte/sec with 3ware
> 9650-8p configured in raid6 and i have 20 mbytes/sec with Compaq Smart Array
> p400 configured in raid5 mode.
> In both raid5/6 configurations, i/o seems stucked as i've reported in my
> previous post with very high iowait values (await up to 5000 ms, svctime up
> to 1000 ms)
> Switching to raid0 / raid10 configurations, totally solved our problems.
> Sync its up to 200mbyte/sec, live i/o seems good as well but i'm still
> testing the vmware infrastructure...
> If anyone has any idea of what's going on....
It seems we have the same problems :-)
After you post, i checked my testing servers and i got surprises:
with a new hp server with P200 controller and 4 disks in raid 5, i get 
max 20mb/s :-(
I checked few things and i didn't find anything wrong in the conf.
We have also another file server with 7 disks in raid 5 and a 3ware card 
  (i think it's a 9550). On that server i got 170 cca mb/s.
I know that hp E200 sure it's not as the 3ware card in term of 
performance, but so low i was not thinking.
I tried different kernels (2.6.18-5 debian, and but 
all the same.
This is a test server and the production servers will have P400 cards
with 512mbyte of cache and i hope this will solve the problem.
I'll try to make some other tests....hope to find find something.


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