6.5.1

Table 1‑102. Disk I/O Performance Enhancement Advice
# Resolution
1 Increase the virtual machine memory. It allows more operating system caching, which reduces I/O activity. Note: It
might require you to increase the host memory. Increasing memory might reduce the need to store data because
databases can utilize the system memory to cache data and avoid disk access.
To verify that virtual machines have adequate memory, check swap statistics in the guest operating system.
Increase the guest memory, but not to an extent that leads to excessive host memory swapping. Install VMware
Tools so that memory ballooning can occur.
2 Defragment the le systems on all guests.
3 Disable antivirus on-demand scans on the VMDK and VMEM les.
4 Use the vendor's array tools to determine the array performance statistics. When too many servers simultaneously
access common elements on an array, the disks might have trouble keeping up. To increase throughput, consider
array-side improvements.
5 Use Storage vMotion to migrate I/O-intensive virtual machines across multiple hosts.
6 Balance the disk load across all physical resources available. Spread heavily used storage across LUNs that are
accessed by dierent adapters. Use separate queues for each adapter to improve disk eciency.
7 Congure the HBAs and RAID controllers for optimal use. Verify that the queue depths and cache seings on the
RAID controllers are adequate. If not, increase the number of outstanding disk requests for the virtual machine by
adjusting the Disk.SchedNumReqOutstanding parameter. For more information, see vSphere Storage.
8 For resource-intensive virtual machines, separate the virtual machine's physical disk drive from the drive with the
system page le. It alleviates disk spindle contention during periods of high use.
9
On systems with sizable RAM, disable memory trimming by adding the line MemTrimRate=0 to the virtual
machine's VMX le.
10 If the combined disk I/O is higher than a single HBA capacity, use multipathing or multiple links.
11 For ESXi hosts, create virtual disks as preallocated. When you create a virtual disk for a guest operating system,
select Allocate all disk space now. The performance degradation associated with reassigning additional disk space
does not occur, and the disk is less likely to become fragmented.
12 Use the most current host hardware.
Disk Requests (Number)
The Disk Requests chart displays disk usage for the virtual machine.
This chart is located in the Home view of the virtual machine Performance tab. It is available only at
collection levels 3 and 4.
vSphere Monitoring and Performance
72 VMware, Inc.