3750 Stack and server backups

Answered Question

Can anyone recommend a best practice for the following scenario?

We currently have a 3750 stack of 9 switches to which all our servers are connected. We have created a vlan (vlan 12 not routed) that we use to connect all the servers that we wish to backup. Lately the server team has seen a drop in backup speed. When we first deployed the stacked switches the backup speed was very slow so TAC support had me apply the following:

mls qos queue-set output 1 threshold 2 3200 3200 100 3200

mls qos queue-set output 1 threshold 3 3200 3200 100 3200

mls qos queue-set output 2 threshold 2 3200 3200 100 3200

mls qos queue-set output 2 threshold 3 3200 3200 100 3200

mls qos

That change worked wonders for the speed issue but now there is slowness again.

There are no errors on ports and the backups stay within the stacked enviroment. There are no other slowness issues with anything else but the nightly backups.

I have this problem too.
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Correct Answer by Joseph W. Doherty about 7 years 7 months ago

Are they 3750Gs? If so, do you realize 3750Gs are not especially high performance switches especially in a maximum stack? Too many concurrent host backups might easily overwhelm the stack ring capacity. (The 32 Gb ring is dual 8 Gb duplex, which, I believe, copies each member switch's packet to every other switch member. [NB: the 3750-E has 2x bandwidth and is much smarter about what it places on the ring and how long it stays on the ring.])

You might check whether some new backup server hosts haven't been recently added and/or existing backup times don't newly overlap (easy to do if backup volume has been increasing).

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Correct Answer
Joseph W. Doherty Thu, 04/23/2009 - 17:04

Are they 3750Gs? If so, do you realize 3750Gs are not especially high performance switches especially in a maximum stack? Too many concurrent host backups might easily overwhelm the stack ring capacity. (The 32 Gb ring is dual 8 Gb duplex, which, I believe, copies each member switch's packet to every other switch member. [NB: the 3750-E has 2x bandwidth and is much smarter about what it places on the ring and how long it stays on the ring.])

You might check whether some new backup server hosts haven't been recently added and/or existing backup times don't newly overlap (easy to do if backup volume has been increasing).

Joseph

I appreciate the response and your headsup on the 3750G verses E. They are G's. The server team did find the source of the slow down so we are good there.

We are a small business with about 1000 employees world wide. And we are not doing voice at this time but we are doing limited video. So I think the 3750G's will do just fine for the present. Should we ever go full blown V&V I'll be looking at a different architecture.

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