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802.1p question

Eric Hutchinson_2
Occasional Advisor

802.1p question

I have a Proliant ml330 with a single nc3123 fast ethernet NIC installed. I use this server to do backups across the network using Arcserve Brightstor 9. I am trying to increase the speed of data to the server. I know that 802.1p will prioritize data, but does it do this for backups? The server is connected to a 3com 3300 switch. The ports can be setup indivdually for 802.1p tagging and the NIC can be also setup for 802.1p tagging. Will this help my backup speed?
Ron Kinner
Honored Contributor

Re: 802.1p question

It might help your backup speed but what would it do to the rest of your network? Normally you use .p for stuff that's realtime like Voice over IP. Seems like it would be a bad idea to give the backup stuff priority over regular traffic. Most people use a separate NIC and network just for backups so they don't have the backups interfering with the real network traffic.

You might also check that you are not getting a lot of collisions or checksum errors on the switch ports. These would indicate a Duplex mismatch (Auto on one side and FUll on the other will always cause a mismatch. Either use FULL FULL or Auto Auto). You could also look into using Jumbo frames if your equipment supports them.

Another possibility would be to put the server in its own vlan and then move the port on the switch that connects to the unit to be backed up into the "backup vlan" just before the backup and then return it to its regular vlan or the default vlan when you are done. You could automate this with a script that telnet to the switch, logs on, makes the changes, logs off, calls the backup, then telnets back into the switch and undoes the changes. This takes the unit off the regular network during the backup but using .p would do virtually the same thing since no one else could get a word in edgewise.

Les Ligetfalvy
Esteemed Contributor

Re: 802.1p question

I have been using ARCserve for years and have long ago come to the conclusion that the bottlenecks always have to do with tweaking ARCserve and almost never with the network hardware. That is not to say that the network design and config does not play a part, but I highly doubt that QOS will be your friend. Look first at tweaking BS AS9 and making sure you have full duplex and the best drivers for the NICs.

I recently put in gig but have not replaced my 100 meg NIC yet in my backup server. I have been monitoring the switch port both on my old 100 meg and now on my new gig network and have been able to drive the NIC to over 90% utilization so the network fabric has never proven to be a bottleneck.

Mind you, to get that sort of throughput, I run multiple parallel backup jobs to separate tape drives on separate SCSI controllers. Depending on your tapes drive technology, it could well be your bottleneck.