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December 10th, 2010 03:00
SRDF syncronous support?
how much lag between writes doesSRDF syncronous support?
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This post is more than 5 years old
2 Intern
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217 Posts
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532
December 10th, 2010 03:00
how much lag between writes doesSRDF syncronous support?
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RRR
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December 10th, 2010 05:00
A few years back I worked for a company that implemented FCIP (Cisco 9216i) and the max lag between the 2 sites was about 6ms MAX. The distance was about 370km and SRDF/S ran without any hickup at all !
modaslam
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December 12th, 2010 23:00
do you have any pdfs which explain how much time and all.
PedalHarder
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December 13th, 2010 17:00
The SRDF/S response time changes over distance because of propegation delay. The longer the distance, the higher amount of time it takes the speed of light to travel. As a rule of thumb for a single round trip, its 1 millisecond per 100KM. IP does single round trip and DMX can do single round trip for FC, but depends on distance and IO size. VMAX always does single round trip for FC. The is a baseline write overhead for SRDF as well, again as a general guide use 1ms.
As an example, you would add 3ms SRDF/S overhead at 200KM for a single round trip
Of course there are many factors that can affect the write response time and the above information is just for the purposes of understanding the relationship between response time vs. distance.
Bear in mind that EMC qualifies SRDF/S to 200KM, so if you are considering a longer distance then it might be a good idea to have a chat to your local EMC rep.