Dell Unity: 2-way NDMP may cause out of memory condition resulting in SP panic or reboot

SP panic due to out of memory condition.

Severe memory fragmentation results in a large memory allocation request to fail resulting in an out-of-memory panic. When using 2-way NDMP, a call to the FCP driver (which sends IO to the safe container) utilizes an IO memory allocation scheme where the memory can become severely fragmented. This eventually (about 4-6 months) results in a large memory allocation request being denied due to the request being larger than the largest free memory and the SP panic is induced.

Work Around
(1) Implement 3-way NDMP.
OR
(2) Scheduling proactive SP reboots every 4-6 months will clear the memory.

Fix
This issue is fixed in Unity OE 5.2.1.0.5.013.

1）What is the difference between 2-way NDMP, and 3-ways NDMP? 
With 2-way NDMP, backup traffic is transferred directly from the Unity primary storage system to the Backup Target System using a zoned Fibre Channel (FC) connection.
With 3-way NDMP, both data and metadata are transferred from the source Unity system over a local area network (LAN) or wide area network (WAN). Data is also transferred through the DMA.

2-way NDMP (There is FC connection to Unity, it will call FCP driver to allocate memory)


3-way NDMP (No FC connection to Unity)


2）Which versions would be impacted by this issue? 
This is a day one issue, it could affect all the Unity array as long as 2-way NDMP is utilized and runs for a long time.

 

Dell EMC Unity XT 380, Dell EMC Unity XT 380F, Dell EMC Unity XT 480, Dell EMC Unity XT 480F, Dell EMC Unity 600, Dell EMC Unity 600F, Dell EMC Unity 650F, Dell EMC Unity XT 680, Dell EMC Unity XT 680F, Dell EMC Unity XT 880, Dell EMC Unity XT 880F , Dell EMC Unity Family, Dell EMC Unity Hybrid ... View More View Less