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Determining the appropriate queue depth for an ESXi host
72 Dell EMC SC Series: Best Practices with VMware vSphere | 2060-M-BP-V
A.2 iSCSI
With 1 Gb SC Series front-end ports, leave the queue depth set to default and only increase if necessary.
With 10 Gb SC Series front-end ports, use the following settings:
• HBA BIOS (if using hardware iSCSI) = 255
• Driver Module (iscsi_vmk) = 255
• DSNRO = 32 (default) (increase or decrease as necessary)
• Guest vSCSI controller = 32 (default) (increase or decrease as necessary)
A.3 Using esxtop to monitor queue depth
The best way to determine the appropriate queue depth is by using the esxtop utility. This utility can be ran
from the ESXi Shell through SSH (command: esxtop), or vCLI 5.x or the vMA virtual appliance (command:
resxtop or resxtop.sh).
When opening the esxtop utility, the best place to monitor queue depth and performance is from the Disk
Device screen. Use the following steps to go to the screen:
1. From the command line, enter one of these two options:
- # esxtop
- resxtop.sh --server esxserver.domain.local
2. Press u to open the Disk Device screen.
3. Type L 36 and press Enter to expand the devices field. This option expands the disk devices columns
to display the volume’s naa identifier.
4. Press f and choose the fields to monitor:
a. Press b to clear the ID field (not needed).
b. Optionally (depending on preference):
i. Check or clear i for overall latency.
ii. Check j for read latency.
iii. Check k for write latency.
c. Press [Enter] to return to the monitoring screen.
5. Type s 2 and press [Enter] to set the refresh time to every 2 seconds.
The quick way to see if the queue depth is set correctly is to monitor the queue depth section along with the
latency section, as shown in Figure 40.
Esxtop with a queue depth of 32