ONTAP and ESXi 6.х tuning

This article will be useful to those who own an ONTAP system and ESXi environment.

ESXi tuning can be divided into the next parts:

  • SAN network configuration optimization
  • NFS network configuration optimization
  • Hypervisor optimization
  • Guest OS optimization
  • Compatibility for software, firmware, and hardware

There are a few documents which you should use when tuning ESXi for NetApp ONTAP:

TR-4597 VMware vSphere with ONTAP

SAN network

In this section, we will describe configurations for iSCSI, FC, and FCoE SAN protocols


ONTAP 9 has ALUA always enabled for FC, FCoE and iSCSI protocols. If ESXi host correctly detected ALUA, then Storage Array Type plug-in will show VMW_SATP_ALUA. With ONTAP it is allowed to use Most Recently Used or Round Robin load balancing algorithm.

Round Robin will show better results if you have more than one path to a controller. In the case of Microsoft Cluster with RDM drives it is recommended to use the Most Recently Used algorithm. Read more about Zoning for ONTAP clusters.

Storage ALUA Protocols ESXi policy Algorithm
Recently Used

Let’s check policy and algorithm applied to a Datastore:

# esxcli storage nmp device list
Device Display Name: NETAPP Fibre Channel Disk (naa.60a980004434766d452445797451376b)
Storage Array Type: VMW_SATP_ALUA
Storage Array Type Device Config: {implicit_support=on;explicit_support=off; explicit_allow=on;alua_followover=on;{TPG_id=1,TPG_state=ANO}{TPG_id=0,TPG_state=AO}}
Path Selection Policy: VMW_PSP_RR
Path Selection Policy Device Config: {policy=rr,iops=1000,bytes=10485760,useANO=0; lastPathIndex=0: NumIOsPending=0,numBytesPending=0}
Path Selection Policy Device Custom Config:
Working Paths: vmhba2:C0:T6:L119, vmhba1:C0:T7:L119
Is Local SAS Device: false
Is USB: false
Is Boot USB Device: false

Ethernet Network

Ethernet network can be used for NFS and iSCSI protocols.

Jumbo frames

Either you are using iSCSI or NFS, it is recommended to use jumbo frames with speed of 1Gbps or greater. When you are setting up Jumbo frames.

ESXi & MTU9000

When you are setting up a virtual machine to achieve the best network performance, so you’d better use VMXNET3 virtual adapter since it supports both speeds greater than 1Gbps and MTU 9000. While E1000e virtual adapter supports MTU 9000 and speeds up to 1Gbps. Also, E1000e by default sets up 9000 MTU to all the VMs except Linux. Flexible virtual adapters support only MTU 1500.

To achieve maximum network throughput, connect your VM to virtual switch which also has MTU 9000.


ONTAP storage systems support VAAI (vSphere Storage APIs Array Integration). VAAI hardware acceleration or hardware offload APIs, is a set of APIs to enable communication between VMware vSphere ESXi hosts and storage devices. So instead of ESXi host copying some data from storage, modifying it in host memory and putting it back to storage over the network, with VAAI some of the operations can be done by storage itself with API calls from ESXi host. VAAI enabled by default for SAN protocols but not for NAS. For NAS VAAI to work you need to install a vib kernel module called NetAppNFSVAAI on each ESXi host. Do not expect VAAI to solve all your problems but some performance definitely will improve. NetApp VSC also can help with NetAppNFSVAAI installation. For NFS VAAI function you have to set your NFS share on storage properly and to meet a few criteria:

  1. On the ONTAP storage set NFS export policy so ESXi servers can access it
  2. RO, RW and Superuser fields must have SYS or ANY values in export policy for your volume
  3. You have to enable NFSv3 AND NFSv4 protocols, even if NFSv4 will not be used
  4. Parent volumes in your junction path have to be readable. In most of the cases, it means that root volume (vsroot) on your SVM needs to have at least superuser field to be set up with SYS. Moreover, it is recommended to prohibit write access to SVM root volume.
  5. Enable vStorage feature has to be enabled for your SVM (vserver)


#cma320c-rtp::> export-policy rule show -vserver svm01 -policyname vmware_access -ruleindex 2
(vserver export-policy rule show)
Vserver: svm01
Policy Name: vmware_access <--- Applied to Exported Volume
Rule Index: 2
Access Protocol: nfs3 <---- needs to be 'nfs' or 'nfs3,nfs4'
Client Match Spec:
RO Access Rule: sys
RW Access Rule: sys
User ID To Which Anonymous Users Are Mapped: 65534
Superuser Security Flavors: sys
Honor SetUID Bits In SETATTR: true

#cma320c-rtp::> export-policy rule show -vserver svm01 -policyname root_policy -ruleindex 1
(vserver export-policy rule show)
Vserver: svm01
Policy Name: root_policy <--- Applied to SVM root volume
Rule Index: 1
Access Protocol: nfs <--- like requirement 1, set to nfs or nfs3,nfs4
Client Match Spec:
RO Access Rule: sys
RW Access Rule: never <--- this can be never for security reasons
User ID To Which Anonymous Users Are Mapped: 65534
Superuser Security Flavors: sys <--- this is required for VAAI to be set, even in the parent volumes like vsroot
Honor SetUID Bits In SETATTR: true
Allow Creation of Devices: true

#cma320c-rtp::> nfs modify -vserver svm01 -vstorage enabled

ESXi host

First of all, let’s not forget it is a good idea to leave 4GB of memory to the hypervisor itself.  Also, we need to tune some network values for ESXi

ProtocolsValues for ESXi 6.x with ONTAP 9.x
NFS41.MaxVolumesNFS 4.1256
NFS.MaxQueueDepthNFS64 (If you have only AFF, then 128 or even 256)

We can do it in a few ways:

  • The easiest way, again, to use VSC which will configure these values for you
  • Command Line Interface (CLI) on ESXi hosts
  • With the GUI interface of vSphere Client/vCenter Server
  • Remote CLI tool from VMware.
  • VMware Management Appliance (VMA)
  • Applying Host Profile

Let’s set up these values manually in command line:

# For Ethernet-based protocols like iSCSI/NFS
esxcfg-advcfg -s 32 /Net/TcpipHeapSize
esxcfg-advcfg -s 512 /Net/TcpipHeapMax

# For NFS protocol
esxcfg-advcfg -s 256 /NFS/MaxVolumes
esxcfg-advcfg -s 10 /NFS/HeartbeatMaxFailures
esxcfg-advcfg -s 12 /NFS/HeartbeatFrequency
esxcfg-advcfg -s 5 /NFS/HeartbeatTimeout
esxcfg-advcfg -s 64 /NFS/MaxQueueDepth

# For NFS v4.1 protocol
esxcfg-advcfg -s 256 /NFS41/MaxVolumes

# For iSCSI/FC/FCoE SAN protocols
esxcfg-advcfg -s 32 /Disk/QFullSampleSize
esxcfg-advcfg -s 8 /Disk/QFullThreshold

And now let’s check those settings:

# For Ethernet-based protocols like iSCSI/NFS
esxcfg-advcfg -g /Net/TcpipHeapSize
esxcfg-advcfg -g /Net/TcpipHeapMax

# For NFS protocol
esxcfg-advcfg -g /NFS/MaxVolumes
esxcfg-advcfg -g /NFS/HeartbeatMaxFailures
esxcfg-advcfg -g /NFS/HeartbeatFrequency
esxcfg-advcfg -g /NFS/HeartbeatTimeout
esxcfg-advcfg -g /NFS/MaxQueueDepth

# For NFS v4.1 protocol
esxcfg-advcfg -g /NFS41/MaxVolumes

# For iSCSI/FC/FCoE SAN protocols
esxcfg-advcfg -g /Disk/QFullSampleSize
esxcfg-advcfg -g /Disk/QFullThreshold


NetApp usually recommends using settings by default. However, in some cases, VMware, NetApp or Application vendor can ask you to modify those settings. Read more in VMware KB. Example:

# Set value for Qlogic on 6.0
esxcli system module parameters set -p qlfxmaxqdepth=64 -m qlnativefc
# View value for Qlogic on ESXi 6.0
esxcli system module list | grep qln


NetApp Virtual Storage Console (VSC) is a free software which helps you to set recommended values for ESXi hosts and Guest OS. Also, VSC helps with basic storage management like datastore creation from vCenter. VSC is a mandatory tool for VVOLs for ONTAP. VSC available only for the vCenter web client supported vCenter 6.0 and newer.

VASA Provider

VASA Provider is a free software which helps your vCenter to know about some specifics and storage capabilities like disk types: SAS/SATA/SSD, Storage Thing Provisioning, Enabled or disabled storage caching, deduplication and compression. VASA Provider integrates with VSC and allows to create storage profiles. VASA Provides also a mandatory tool for VVOLs. NetApp VASA, VSC and Storage Replication Adapter for SRM are bundled in a single virtual appliance and available for all NetApp customers.

Space Reservation — UNMAP

UNMAP functionality allows to free space on datastore and storage system after data been deleted from VMFS or inside Guest OS, this process known as space reclamation.  There are two independent processes:

  1. First space reclamation form: ESXi UNMAP to storage system when some data been deleted from VMFS datastore. For this type of reclamation to work, storage LUN has to be thin provisioned, and space allocation functionality needs to be enabled on the NetApp LUN. Reclamation of this type can happen in two cases:
    • A VM or VMDK has been deleted
    • Data deleted from Guest OS file system and space reclaimed on from Guest OS VMFS. Basically, after the UNMAP form, Guest OS already happened.
  2. Second space reclamation form: UNMPA from Guest OS when some data deleted on Guest OS file system to free space on VMware datastore (either NFS or SAN). This type of reclamation has nothing in to do with the underlying storage system and do not require any storage tuning or setup, but does need Guest OS tuning and some additional requirements for this feature to function.

Both space reclamation forms are not tied one to another, and you can have only one of them set up to work, but for the best space efficiency, you are interested in having both.

First space reclamation form: From ESXi host to storage system

Historically VMware introduced only the first space reclamation form: from VMFS to storage LUN in ESXi 5.0 with space reclamation happened automatically and nearly online. Moreover, it wasn’t the best idea because it immediately hit storage performance. So, with 5.X/6.0 VMware disabled automatic space reclamation and you have to run it manually. ESXi 6.X with VVOLs space reclamation works automatically and with ESXi 6.5 and VMFS6 it also works automatically, but in both cases,  it is asynchronously (not online process).  

On ONTAP space reclamation (space allocation) is always disabled by default:

lun modify -vserver vsm01 -volume vol2 -lun lun1_myDatastore -state offline

lun modify -vserver vsm01 -volume vol2 -lun lun1_myDatastore -space-allocation enabled lun modify -vserver vsm01 -volume vol2 -lun lun1_myDatastore -state online

If you are using an NFS datastore, space reclamation not needed, because with NAS this functionality available by design. UNMAP needed only for SAN environment because it definitely was one of the disadvantages to NAS.

This type of reclamation automatically occurs in ESXi 6.5 during up to 12 hours and can also be initiated manually.

esxcli storage vmfs reclaim config get -l DataStoreOnNetAppLUN
Reclaim Granularity: 248670 Bytes
Reclaim Priority: low esxcli storage vmfs reclaim config set -l DataStoreOnNetAppLUN -p high

Second space reclamation form: UNMPA from Guest OS

Since for VMs VMDK file is basically a block device, you can apply UNMAP mechanism there too. Starting from 6.0 VMware introduced such capability. It started with Windows in the VVOL environment with ESXi 6.0 with automatic space reclamation from Guest OS and manual space reclamation with Windows machines on ordinary datastores. Later introduced automatic space reclamation from Guest OS (Windows and Linux) on ordinary Datastores in ESXi 6.5.

Now to set it up to function properly it might be trickier then you think. The hardest thing to make this UNMAP work is just to comply with requirements. Once you comply with the requirements, it is easy to make it happen. So, you need to have:

  • Virtual Hardware Version 11
  • vSphere 6.0*/6.5
  • VMDK disks must be thin provisioned
  • The file system of the Guest OS must support UNMAP
    • Linux with SPC-4 support or Windows Server 2012 and later

* If you have ESXi 6.0, then CBT must be disabled, which means in a real production environment you are not going to have Guest OS UNMUP since no production can live without proper backups (Backup software leverage CBT for backups to function)

Moreover, if we are adding ESXi UNMAP to the storage system, a few more requirements needed to be honored:

  • LUN on the storage system must be thinly provisioned (in ONTAP it can be enabled/disabled on the fly)
  • Enable UNMAP in ONTAP
  • Enable UNMAP on Hypervisor

Never use Thin virtual disks on Thin LUN

For many years storage all vendors stated not to use thin virtual disks on thin LUNs, and now it is a requirement to make space reclamation from Guest OS.


UNMAP supported in Windows starting with Windows Server 2012. To make Windows reclama space from VMDK, NTFS must use allocation unit equal to 64KB. To check UNMAP settings issue next command:

fsutil behavior query disabledeletenotify

DisableDeleteNotify = 0 (Disabled) means UNMUP is going to report to the hypervisor to re-clame space.

Linux Guest OS SPC-4 support

Let’s check first is our virtual disk thin or thick:

sg_vpd -p lbpv
Logical block provisioning VPD page (SBC):
Unmap command supported (LBPU): 1

1 means we have a thin virtual disk. If you got 0, then your virtual disk either thick (sparse or eager), both are not supported with UNMAP. Let’s go farther and check that we have SPC-4

sg_inq -d /dev/sda
standard INQUIRY:
PQual=0 Device_type=0 RMB=0 version=0x06 [SPC-4]
Vendor identification: VMware
Product identification: Virtual disk
Product revision level: 2.0

We need to have SPC-4 to make UNMAP work automatically. Let’s check Guest OS notifying SCSI about reclaimed blocks

grep . /sys/block/sdb/queue/discard_max_bytes

1 means we are good. Now let’s try to create a file, remove it and see if we get our space freed:

sg_unmap --lba=0 --num=2048 /dev/sda
# or
blkdiscard --offset 0 --length=2048 /dev/sda

If you are getting “blkdiscard: /dev/sda: BLKDISCARD ioctl failed: Operation not supported”, then UNMAP doesn’t work properly. If we do not have an error, we can remount our filesystem with “-o discard” key to make UNMAP automatic.

mount /dev/sda /mnt/netapp_unmap -o discard

Guest OS

You need at least to check your Guest OS configurations for two reasons:

  1. To gain max performance
  2. To make sure in case of one controller down, your Guest OS survive takeover timeout

Disk alignment: to make sure you get max performance

Disk Misalignment is an infrequent situation, but you still you may get into it. There are two levels where you can get this type of problem:

  1. When you created a LUN in ONTAP with geometry, for example, Windows 2003 and then used it with Linux. This type of problem can occur only in a SAN environment. Its very simple to avoid when you are creating a LUN in ONTAP, make sure you chose proper LUN geometry. This problem happens between storage and hypervisor
  2. Inside of a virtual machine. It can happen in SAN and NAS environment.

To understand how it works let’s take a look on a properly aligned configuration

Fully aligned configuration

On this image upper block belong to Guest OS, block in the middle belongs to ESXi, and lower block represents ONTAP storage system.

First case: Misalignment with VMFS

When you have your VMFS file system misaligned with your storage system. Also, that will happen if you create on ONTAP a LUN with geometry not equal to VMware. It is very easy to fix: just create a new LUN in ONTAP with VMware geometry, create new VMFS datastore and move your VMs to the new one, destroy old one.

Second case: Misalignment inside your guest OS

This is also a very rare problem which can occur because you can get this problem with very old Linux distributives, Windows 2003 and older. However, we are here to discuss all the possible problems to understand better how it works, right? This type of problem can occur on NFS datastore and VMFS datastore leveraging SAN protocols, also in RDM and VVOLs. This type of problem usually happens with virtual machines using non-optimally aligned MBR on Guest OS or Guest OS which previously were converted from physical machines to virtual. How to identify and fix misaligned in Guest OS you can find in NetApp KB.

Misalignment on two levels simultaneously

Of course, if you are very lucky, you can get both simultaneously: on VMFS level and Guest OS level. Later in this article, we will discuss how to identify such a problem from the storage system side.


NetApp ONTAP storage systems consist of one or a few building blocks called HA pairs. Each HA pair consists of two controllers and in the event of one controller failure of one controller, second will take over and continue to serve clients. The takeover is a relatively fast process in ONTAP, and in new All-Flash FAS (AFF) configurations it takes from 2 to 15 seconds. However, with hybrid FAS systems, this time can be longer and take up to 60 seconds. 60 seconds is the absolute maximum after which NetApp guarantees failover to be completed in FAS systems, and it usually occurs for 2-15 seconds. This numbers should not scare you in any way, because during this time your VMs will survive, as long as your timeouts are set equals to or greater than 60 sec and default VMware Tools value for your VMs is 180 seconds in any way. Moreover, since your ONTAP cluster can have different models, generations and disk types of systems, it is a good idea to use the worst-case scenario which is 60 sec.

Guest OSUpdated Guest OS Tuning for SAN:
ESXi 5 and newer, or ONTAP 8.1 and newer (SAN)
Windowsdisk timeout = 60
Linuxdisk timeout = 60

Default values for Guest OS on NFS datastores are tolerable, and there is no need to change them. However, I would recommend testing a takeover in any way to be sure how it works at such events.

You can configure these values manually or with the use of NetApp Virtual Storage Console (VSC) utility. NetApp Virtual Storage Console (VSC) provides the scripts to help reduce the efforts involved in manually updating the guest OS tunings.


You can change Windows registry and reboot Guest OS. Timeout in Windows set in seconds in hexadecimal format.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Disk] “TimeOutValue”=dword:0000003c


Timeout in Linux set in seconds in decimal format. To do that you need to modify udev rule in your Linux OS. Location for udev rules may vary from one Linux distributive to another.

# RedHat systems
ACTION=="add", BUS=="scsi", SYSFS{vendor}=="VMware, " , SYSFS{model}=="VMware Virtual S", RUN+="/bin/sh -c 'echo 60 >/sys$DEVPATH/device/timeout'"

# Debian systems
ACTION=="add", SUBSYSTEMS=="scsi", ATTRS{vendor}=="VMware " , ATTRS{model}=="Virtual disk ", RUN+="/bin/sh -c 'echo 60 >/sys$DEVPATH/device/timeout'"

# Ubuntu and SUSE systems
ACTION=="add", SUBSYSTEMS=="scsi", ATTRS{vendor}=="VMware, " , ATTRS{model}=="VMware Virtual S", RUN+="/bin/sh -c 'echo 60 >/sys$DEVPATH/device/timeout'"

VMware tools automatically sets udev rule with timeout 180 seconds. You should go and double check it with:

find /sys/class/scsi_device/*/device/timeout -exec grep -H . '{}' \;


NetApp has Interoperability Matrix Tool (IMT), and VMware has the Hardware Compatibility List (HCL). You need to check on them and stick to the versions both vendors support to reduce potential problems in your environment. Before any upgrades make sure, you are always staying in the compatibility list.


Most of this article are theoretical knowledge which most probably you will not need because nowadays nearly all parameters either automatically assigned or set as default configuration and very possible you will not see misalignment in new installations in real life, but if something will go wrong, information in this article will shed light on some of the under-hood aspects of ONTAP architecture and will help you to deep dive & figure out the reasons of your problem.

Correct settings for your VMware environment with NetApp ONTAP gives not just better performance but also ensure you will not get into trouble in the event of storage failover or network link outage. Make sure you are following NetApp, VMware and application recommendations. When you are setting up your infrastructure from scratch always test performance and availability, simulate storage failover and network link outage. Testing will help you to understand your infrastructure baseline performance, behavior in critical situations and help to find week points. Stay in compatibility lists, it will not guarantee yuo never get in to troubles, but reduce risks and keep you supportable by the both vendors.

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