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Occasional Contributor
Posts: 11
Registered: ‎07-02-2008

Brocade 48000 BB_Credit Zero reporting high numbers

We are seeing a high number of BB_Credit Zero number for a specific port, host to storage when that host runs an "R-Man backup.

The setup:

2 Brocade Directors 48000 class, (A - side and B - side)

storage is on an IBM FastT, (4300 express) through a SVC.

Cache settings on the FastT are set for read and write and the cache block size set to 16k

Currently to write a 64GB backup it is taking about 60 minutes.

Two questions.

1 - Is this normal operation?

That is to see high valu in the BB_Credit Zero when the rman is running

2 - Is there anything I can do to correct this?

Thank you

Super Contributor
Posts: 260
Registered: ‎04-09-2008

Re: Brocade 48000 BB_Credit Zero reporting high numbers

You need to give some idea of the topology before I can think on what can be done.

Two questions.

1 - Is this normal operation?That is to  see high valu in the BB_Credit Zero when the rman is running

I wouldnt worry too much if the counter is rising on a F port. I usually track these stats on a E port only. However if there is too much depletion of BB credits on a particular port, it can cause problems such as drop of frames etc. and cause IO timeouts.

2 - Is  there anything I can do to correct this?

If you provide me an idea of the topology then I can try giving some suggestions. Increasing locality can help sometimes.

The 4300 is not a very powerful storage and hence you can't expect too much out of it. Also note that backup performance depends on a variety of factors and most times you need to look at the backup host or the host itself for answers.

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