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тАО08-10-2004 06:33 AM
тАО08-10-2004 06:33 AM
Here are some Fiber Channel transfer rate ratings:
..EMC FA:........................2 Gbit/sec
..EMC Connectrix Switch Port:....2 Gbit/sec
..HP-UX FC HBA:................200 MBytes/sec
Of course they rate them in different units. Since I only care about Bytes, I have to convert 2 Gb/s to MB/s, where:
..B - Byte
..b - bit
gives me:
..2 Gb/s * 1000 Mb/Gb
..------------------------ = 250 Mbytes/sec
.........8b/B
So, the FA is 250 MBytes/sec and the HBA is 200 MBytes/sec.
So, how can I have a "Fan-In" ratio of UNIX server HBAs to FAs of 6 to 1?
Are there "utilization" stats like an HBA is only 75% efficient and they only run 60% of the time?
do you divide by 8 to convert bits to bytes? Or do you divide by some other number (start/stop bits?)?
Is there some explanation for figureing this somewhere?
..EMC FA:........................2 Gbit/sec
..EMC Connectrix Switch Port:....2 Gbit/sec
..HP-UX FC HBA:................200 MBytes/sec
Of course they rate them in different units. Since I only care about Bytes, I have to convert 2 Gb/s to MB/s, where:
..B - Byte
..b - bit
gives me:
..2 Gb/s * 1000 Mb/Gb
..------------------------ = 250 Mbytes/sec
.........8b/B
So, the FA is 250 MBytes/sec and the HBA is 200 MBytes/sec.
So, how can I have a "Fan-In" ratio of UNIX server HBAs to FAs of 6 to 1?
Are there "utilization" stats like an HBA is only 75% efficient and they only run 60% of the time?
do you divide by 8 to convert bits to bytes? Or do you divide by some other number (start/stop bits?)?
Is there some explanation for figureing this somewhere?
Solved! Go to Solution.
3 REPLIES 3
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тАО08-10-2004 07:12 AM
тАО08-10-2004 07:12 AM
Solution
2 GigaBits/second is exactly 2.125 GigaBits/second on the cable. This includes the overhead in a fibre channel frame.
Now, any 8-bit 'data byte' is sent on the cable as a 10-bit 'transmission character'. It is for self-clocking, error detection and DC balance of the receiver.
So, 2 GigaBites/sec = 200 MegaByte/sec = user data bandwidth.
Now, any 8-bit 'data byte' is sent on the cable as a 10-bit 'transmission character'. It is for self-clocking, error detection and DC balance of the receiver.
So, 2 GigaBites/sec = 200 MegaByte/sec = user data bandwidth.
.
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тАО08-10-2004 09:51 AM
тАО08-10-2004 09:51 AM
Re: HBA Transfer Rate Calcucations
Uwe:
That's perfect for part 1 of my question.
But, how does "Fan In" work, if hte HBA and FA (on the EMC) are the same speed?
There must be some empiracal (sp?) evidence which states that a single server only drives the HBA/FA at XX% capacity...
That's perfect for part 1 of my question.
But, how does "Fan In" work, if hte HBA and FA (on the EMC) are the same speed?
There must be some empiracal (sp?) evidence which states that a single server only drives the HBA/FA at XX% capacity...
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тАО08-10-2004 06:01 PM
тАО08-10-2004 06:01 PM
Re: HBA Transfer Rate Calcucations
Oh, that's a good question...
I have heard about values of 7:1 for 1 GigaBit and 14:1 for 2 GigaBit storage networks as a 'rule of thumb'.
Sounds OK as many servers are not really bandwidth-hungry - they need I/Os.
I have heard about values of 7:1 for 1 GigaBit and 14:1 for 2 GigaBit storage networks as a 'rule of thumb'.
Sounds OK as many servers are not really bandwidth-hungry - they need I/Os.
.
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