[DRBD-user] Read Performance Issues

J. Ryan Earl oss at jryanearl.us
Wed Feb 2 21:01:27 CET 2011

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


You're probably FSB bound.  Without DRBD you're probably doing direct DMA
transfers that don't affect your FSB.   You need to split the memory and I/O
traffic so they're not on the same bus.  You'd do better with a CPU that has
an integrated memory controller and separate I/O channels.  The performance
you're seeing isn't bad for your hardware.

-JR

On Mon, Jan 31, 2011 at 6:11 PM, Mark Petersen <mpetersen at peak6.com> wrote:

> Hi,
>
>
>
> I’m trying to use DRBD with the backend storage on a FusionIO device (NAND
> Flash without disk controller overhead.)  I’ve found that I’m taking a huge
> performance hit via testing with fio.
>
>
>
> IOPS
>
> `fio --directory=/fio/test --direct=1 --rw=randread --bs=4k --size=5G
> --numjobs=64 --runtime=10 --group_reporting --name=file1`
>
> raw device: 104k
>
> drbd device: 75k
>
>
>
> Bandwidth
>
> `fio --directory=/fio/test --direct=1 --rw=randread --bs=1m --size=5G
> --numjobs=4 --runtime=100 --group_reporting --name=file1`
>
> raw device: 750 MB/s
>
> drbd device: 550-600 MB/s
>
>
>
> I’ve tried drbd 8.3.9 and 8.3.10 and while 8.3.10 might be slightly better,
> it’s mostly insignificant (1-2%.)
>
>
>
> The backend for writing is 2 x 1GB bonded round robin dedicated interfaces,
> but since I’m seeing a read hit I’m not concerned with this potential write
> bottle neck at the moment unless it’s somehow related, I plan to use 10 gig
> cards in the near future if this works out.
>
>
>
> ?  The DRBD process seems be CPU bound, but performance is worse if I
> change cpu affinity to be more than 1 core.  This is on a E5430  @ 2.66GHz.
> I imagine a faster CPU could improve performance, but I’m looking for other
> suggestions of course.
>
> Other Relevant Details:
>
> CentOS 5.5
>
> Kernel 2.6.18-194
>
> Filesystem XFS
>
> drbd 8.3.9 and 8.3.10 compiled into rpm’s from source (any compile time
> tweaks I could use, such as CPU type?)
>
>
>
> Thanks,
>
> Mark
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