Re: Curiosity question - Bandwidth using RMAN duplicate from Serivce

From: Mladen Gogala <gogala.mladen_at_gmail.com>
Date: Wed, 27 Feb 2019 21:16:13 -0500
Message-ID: <db2aa9ec-bb01-6c63-8752-93b5c2b704ba_at_gmail.com>

Hi Chris!

One channel on a physical Linux box  typically does around 350 GB/hr when compression is used. It's around 7.5 MB/sec. Incidentally, that is also a 1Gb NIC bandwidth. If you have a 10 Gb network, these number scale pretty much linearly. On a 10 GB network, with 10 channels you can

achieve around 3.5 TB/hr. That will devour the entire 10Gb connection, 
so I wouldn't go above 8. You can also have an Infiniband, which 
provides up to 40 Gb/sec. You will frequently find storage connected by 

Infiniband when using Exadata. That would achieve around 15 TB/hour. That would achieve the throughput  of around 15 TB/hr, which means that you would backup 100 TB database in approximately 7 hours. There are also faster, 100 Gb network connection, which are very useful for backing up 100+ TB databases. On a full rack Exadata, that would mean 16 channels per node.

However, for a  more precise information, I would need to know the kind of computer you're connecting  to and its writing speed. If the connection target is using some cheapo NAS as the backup storage, more than likely, the best you can do is a 10 Gb connection. It is also important to know what backup system is being used. I have a lot of experience with Commvault and the numbers reported are for Commvault.

FULL DISCLOSURE: I am an employee of Commvault Systems.

Regards

On 2/27/19 6:34 PM, Chris Taylor wrote:
> If you're doing a duplicate from a service_name to a clone, can one
> channel use all the available bandwidth between the 2 hosts?
>
> I don't know of any reason why a channel itself would be throttled.
> I can understand a channel not being able to read enough from disk to
> fill up the network card, so I'm guessing in theory 1 channel could
> use all the available bandwidth if it was reading from disk fast enough?
>
> Key question:
> I wonder how you could determine the correct number of channels if you
> know your disk read rate to avoid hammering your network bandwidth
> going out of the server?
>
> (Note:  I recently pegged a network card on a production server doing
> an RMAN duplicate and I've been puzzling over this since then -
> doesn't help that our production server had one network card only)
>
> Chris
>

-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217


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Received on Thu Feb 28 2019 - 03:16:13 CET