NetWare and Hyperthreading, again

I talked about this one last year during some benchmarking. I just had a classic case crop up today.

It has long been consensus in the support forums that, (paraphrased) "If you have hyperthreading turned on and get an I/O thread stuck on a logical process, woe be unto you."

I have a server that I've been backing up for a fellow admin in another department. This particular server has 525GB of storage to back up, so it's going to take some time. It has been vexing figuring this one out. Until today, when I finally twigged to the fact that this server has HT turned on. I turn HT off as almost the first thing I do when setting up a server, so I don't think about it when troubleshooting.

Between 1000 and 1215 today, the backup got 882MB of data. Yeah, very crappy.

At 1215 I turned off the logical processors. This is a handy feature NetWare has, and I used it in the article I linked above.

At 1222 when I checked back the backup was up to 4.0GB.

At 1417 it is now up to 71GB backed up.

The only thing that changed was me turning off the logical processors. That's it. At that rate, this server should be backed up in around 15 hours, which is a far cry from the 30+ hours it was doing before.

Turn Hyperthreading off on your NetWare servers. Just do it.