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Difference between SRDF Synchronous and SRDF Asynchronous
Hi Team,
please help me by providing the major difference between SRDF/S and SRDF/A.
and also please let know on which situation thease two are used.
satheeshnp
11 Posts
0
May 2nd, 2013 05:00
In synchronous mode (SRDF/S), the primary array waits until the secondary array has acknowledged each write before the next write is accepted, ensuring that the replicated copy of the data is always as current as the primary. However, the latency due to propagation increases significantly with distance.
Asynchronous SRDF (SRDF/A) transfers changes made to the secondary array in units called delta sets, which are transferred at defined intervals. Although the remote copy of the data will never be as current as the primary copy, this method can replicate data over considerable distances and with reduced bandwidth requirements and minimal impact on host performance.
Avinash V
91 Posts
0
May 2nd, 2013 05:00
You could refer to the SRDF Connectivity Guide available at -
https://support.emc.com/docu6182_Symmetrix-Remote-Data-Facility-(SRDF)-Connectivity-Guide.pdf
Page 20 & Page 23
seancummins
226 Posts
1
May 2nd, 2013 05:00
SRDF/S is Synchronous -- the remote volumes are always 100% identical to the local volumes with no lag time, giving you a Recovery Point Objective of zero. With sync replication your applications must wait for every write to be acknowledged by both the local and the remote arrays, so they are subject to the latency of the network link between the two arrays. Latency is higher when distances are greater, so sync replication can only be accomplished over relatively short distances.
SRDF/A is Asynchronous -- the remote volumes lag slightly behind the local volumes, so the applications do not "feel" the latency of the network link, enabling async replication over longer distances. We insulate applications from the effect of network latency by buffering the replication in Symmetrix cache. The remote volumes still contain consistent point-in-time copies of data (as a result of cache buffering), but those points in time are slightly behind the production volumes -- typically on the order of 15-30 seconds behind. So in this case, your RPO isn't quite zero, but you can replicate over longer distances.
V_M_Ramkumar
97 Posts
0
May 13th, 2013 01:00
we will get a Gold Copy of data in Asynchronous as well?
i know we will get gold copy for Synchronous?