ESXi 6.5 Storage Performance Issues and Fix
[NOTE] : I decided to republish this post with a new heading and skip right to the meat of the issue as I’ve had a lot of people reach out saying that the post helped them with their performance issues on ESXi 6.5. Hopefully people can find the content easier and have a fix in place sooner.
The issue that I came across was to do with storage performance and the native driver that comes bundled with ESXi 6.5. With the release of vSphere 6.5 yesterday, the timing was perfect to install ESXI 6.5 and start to build my management VMs. I first noticed some issues when uploading the Windows 2016 ISO to the datastore with the ISO taking about 30 minutes to upload. From there I created a new VM and installed Windows…this took about two hours to complete which I knew was not as I had expected…especially with the datastore being a decent class SSD.
I created a new VM and kicked off a new install, but this time I opened ESXTOP to see what was going on, and as you can see from the screen shots below, the Kernel and disk write latencies where off the charts topping 2000ms and 700-1000ms respectively…In throuput terms I was getting about 10-20MB/s when I should have been getting 400-500MB/s.
ESXTOP was showing the VM with even worse write latency.
I thought to myself if I had bought a lemon of a storage controller and checked the Queue Depth of the card. It’s listed with a QD of 31 which isn’t horrible for a homelab so my attention turned to the driver. Again referencing the VMware Compatibility Guide the listed driver for the controller the device driver is listed as ahci version 3.0.22vmw.
I searched for the installed device driver modules and found that the one listed above was present, however there was also a native VMware device drive as well.
[root@LAB-ESXI-01:~] esxcli software vib list | grep ahci
sata-ahci 3.0-22vmw.6220.127.116.1164106 VMW VMwareCertified 2016-11-16
vmw-ahci 1.0.0-32vmw.618.104.22.16864106 VMW VMwareCertified 2016-11-16
I confirmed that the storage controller was using the native VMware driver and went about disabling it as per this VMwareKB (thanks to @fbuechsel who pointed me in the right direction in the vExpert Slack Homelab Channel) as shown below.
[root@LAB-ESXI-01:~] esxcli system module set --enabled=false --module="vmw_ahci"
[root@LAB-ESXI-01:~] esxcli system module list | more
Name Is Loaded Is Enabled
----------------------------- --------- ----------
vmkernel true true
chardevs true true
user true true
vmkapi_v2_1_0_0_vmkernel_shim true true
vmkusb true true
igbn true true
vmw_ahci true false
iscsi_trans true true
iscsi_trans_compat_shim true true
vmkapi_v2_2_0_0_iscsiInc_shim true true
After the host rebooted I checked to see if the storage controller was using the device driver listed in the compatibility guide. As you can see below not only was it using that driver, but it was now showing the six HBA ports as opposed to just the one seen in the first snippet above.
I once again created a new VM and installed Windows and this time the install completed in a little under five minutes! Quiet a difference! Upon running a crystal disk mark I was now getting the expected speeds from the SSDs and things are moving along quiet nicely.
Hopefully this post saves anyone else who might by this, or other SuperMicro SuperServers some time and not get caught out by poor storage performance caused by the native VMware driver packaged with ESXi 6.5.