Thursday, August 31, 2006

We have finally killed off our DPM at Edinburgh! The machine has been reinstalled with SL4.3 and once the DNS has been changed to reflect the new hostname we will configure it as a second dCache pool node. In parallel with the reinstall we reconfigured the site so use our dCache as the default SE. According to gstat, so far, so good but we are still waiting for the first SFT to run.

The new dCache pool node will be connected to about 12TB of disk and since it will run a GridFTP door, we should be able to sustain higher bandwidths into the site than are currently possible. Now need to look at running xfs on the disk pools which we know will give additional gains in performance. Initial tests on a test node have shown the problems with xfs on SL4 to have been solved if the latest (2.6.9-34.0.2) kernel is used.

Next on the dCache todo list is finding a suitable way to utilise the SAN storage across NFS. Using it as a disk based HSM is a possibility but then no one has done this before....


Graeme Stewart said...

Are you running this as i386 or x86_64? My tests with x86_64 and DPM have been a bit of a flop, alas, but i386 works ok.

I'm probably not going to go with xfs because of the 4k stacks issue. I'm swithering between ext3 (the safe choice) and jfs (which should give better performance).

Greig A Cowan said...

It's running as i386. I haven't changed the stack size from the default. All I did was install the latest kernel and get the corresponding xfs kernel modules from the SL4.3 repo. The test system survived a few different benchmark tests. I was thinking of running a comparison on our production hardware between ext3 and xfs to see if running xfs like this will give any sort of performance boost. However, it may turn out that there is only a performance gain if the kernel is recompiled to use 8K stacks. Thoughts?