In a synchronous SnapMirror configuration, the source storage appliance exhibits high latency due to user traffic and rapid data change from…

In a synchronous SnapMirror relationship, a write I/O on the source volume is not acknowledged to the client until the data is successfully committed on both the source and destination volumes. High latency on the source is therefore directly influenced by the destination's ability to process and acknowledge these writes. The outstanding parameter, used in snapmirror.conf on older ONTAP systems, limits the number of concurrent transfers in the queue. By setting a lower limit (throttling), it prevents the source from overwhelming the destination with write requests. This allows the destination to maintain lower, more consistent write latency, which in turn reduces the overall latency experienced by the client on the source system.

B. visibilityinterval=3s: This parameter is specific to SnapVault relationships and controls how often newly transferred data becomes visible on the destination. It does not affect source-side performance latency.

C. cksum=3s: The cksum parameter is used to define the data integrity checksum algorithm for the transfer. It is not a primary performance tuning tool for latency, and the syntax 3s is invalid.

D. src con=3: This is not a valid or recognized parameter within the snapmirror.conf file for tuning SnapMirror relationships.

1. NetApp Technical Report TR-4015

"SnapMirror Configuration and Best Practices Guide for ONTAP 9.1

9.2": Section 4.1

"Synchronous SnapMirror

" describes the synchronous write path: "The write is not acknowledged back to the client or application until the data is written to the destination volume as well as the source volume." This principle underpins why destination performance directly impacts source latency

making a throttling mechanism like outstanding the relevant solution.

2. NetApp ONTAP 9 Documentation

"Data protection power guide": The section "Performance considerations for synchronous relationships" states

"The performance of the primary storage system is affected by the performance of the secondary storage system and the latency of the network that connects them." This supports the rationale for tuning the interaction between the source and destination to manage performance.

3. NetApp ONTAP Documentation

"Commands: Manual Page Reference": The manual pages for the snapmirror.conf file (in relevant 7-Mode and early cDOT versions) detail valid parameters. While outstanding is an obscure or older parameter

the other options are verifiably incorrect for this scenario. For example

visibilityinterval is explicitly tied to SnapVault (qtree based SnapMirror) and not synchronous replication.