[DRBD-user] Read Performance Issues

Mark Petersen mpetersen at peak6.com
Tue Feb 1 01:11:14 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.


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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