----- Original Message ----- > From: "Shariq Siddiqui" <shariq.siddiqui@xxxxxxxxx> > To: linux4oracle@xxxxxxxxxxxxxxx, linux-cluster@xxxxxxxxxx > Sent: Wednesday, 16 February, 2011 12:04:00 PM > Subject: RAW Devices performance issue > Dear All, > > I am going to install Oracle RAC on two Servers, With shared SAN > storage (Servers and Storage is IBM) > OS = RHEL 5u5 x64 bit > > And we used multipathing mechanism and created multipathing devices. > i.e. /dev/mapper/mpath1. > > Then I created raw device /dev/raw/raw1 of this /dev/mapper/mpath1 > Block device as per pre-reqs for Oracle Cluster. > > Every thing looks good, But we faced the performance issue as under... > > when we run command : > #dd if=/dev/zero of=/dev/mapper/mpath1 bs=1024 count=1000 > the writing rate is approx. 34 MB/s > > But If we run command > #dd if=/dev/zero of=/dev/raw/raw1 bs=1024 count=1000 > the writing rate is very slow like 253 KB/s > > Please advice how to tune the performance. Hi, I dont know anything about using raw devices, but I do know the write speed through the multipath device for the SAN is slow. Try fix that performance first - check SAN cache write is enabled, check your raid levels and over how many disks. I cant say what you should get, but i've seen local non raided disks write much faster Stefan -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
