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Dell PowerEdge Systems Red Hat Enterprise Linux 8 Release Notes

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Dell EMC OpenManage Storage Services utility fails to reconfigure the virtual disk

Description
On a system with multiple guest VMs running storage IO and network IO operations, Dell EMC OpenManage Storage Services utility fails to reconfigure the virtual disk that is connected to the PERC H755 or PERC H755N card. The dmesg displays following call trace indicating page allocation failure for high order memory allocation requests: 
dsm_sa_datamgrd: page allocation failure: order:6, mode:0x6000c0(GFP_KERNEL), nodemask=(null),cpuset=/,mems_allowed=0-1
dmesg also shows following messages: 
megaraid_sas 0000:01:00.0: Failed to alloc kernel SGL buffer for IOCTL
megaraid_sas 0000:01:00.0: Failed to alloc kernel SGL buffer for IOCTL
The issue may occur when the operating system is under pressure for high-order memory.
Workaround
Reconfigure the virtual disk from the Integrated Dell Remote Access Controller (iDRAC).
Cause
By default, the 'cache' setting for VMs is set to writeback. This results in host memory being used for buffer cache when storage IO is being performed by guest VMs.
Solution
Modify the 'cache' setting for guest VMs to 'none'. For more information, see Red Hat Enterprise Linux Knowledge Base article 5905701.
In the XML profile of guest VMs, change the following: 
<disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
To 
<disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
Systems affected
All Dell EMC PowerEdge servers
Applies to
Red Hat Enterprise Linux 8.3
Tracking number
194332

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