Jumbo Frames Usage for DDBoost

PURPOSE

This KB talks about the points to be considered while using the jumbo frames in DDBoost Backups and Replication.

SYMPTOMS

• Backups having performance issue
• Connection reset
• Experiencing retransmissions

APPLIES TO

• All Data Domain systems
• All Software Releases
• DDBOOST/OST

CAUSE

Mismatch in the frame size and incompatible network cards.

SOLUTION

Usage of Jumbo Frames for the DDBOOST backups and replication

• For DDBoost backups, the recommendation would be to use 1500 MTU because no performance improvement has been seen using 9000 MTU.
• Even though DDBoost uses TCP functions it can be impacted by the application and the network Environment.
• If the network environment does not support 9000 byte packets, the size will be reduced to the size that it can handle, but with potentially multiple paths this may not be conveyed adequately to the TCP connection which will cause the connection to fail.
• In case of a connection failure DDBoost will open another connection and continue to try but this will result in more than expected connections to be seen.
• DDR does not allow fragmentation of the packets so if they are too large the connection will fail.
• For the OPT_DUP jobs going over WAN it is always recommended to use 1500 MTU.