Multipath iSCSI for VMware in IBM Cloud

Today we’re really going to go down the rabbit hole. Although there was not a great deal of fanfare, earlier this year IBM Cloud released support for up to 64 VMware hosts to attach an Endurance block storage volume using multipath connections. In order to use multipath, this requires the use of some APIs that are not well documented. After a lot of digging, here is how I was able to leverage this support.

First, your account must be enabled for what IBM Cloud calls “iSCSI isolation.” All new accounts beginning in early 2020 have this enabled. You can check whether it is enabled using the following Python script:

# Connect to SoftLayer
client = SoftLayer.Client(username = USERNAME, api_key = API_KEY, endpoint_url = SoftLayer.API_PUBLIC_ENDPOINT)

# Assert that iSCSI isolation is enabled
isolation_disabled = client['SoftLayer_Account'].getIscsiIsolationDisabled()
assert isolation_disabled == False

iSCSI isolation enforces that all devices in your account are using authentication to connect to iSCSI. In rare cases, some accounts may be using unauthenticated connections. If the above test passes, your account is ready to go! If the above test fails, you should first audit your usage of iSCSI connections to ensure they are all authenticated. Only if the above test fails and you have verified that either you are not using iSCSI, or all of your iSCSI connections are authenticated, then open a support ticket as follows. Plan for this process to take several days as it requires internal approvals and configruation changes:

Please enable my account for iSCSI isolation according to the standard block storage method of procedure.

Thank you!

Once the above test for iSCSI isolation passes, we are good to proceed. We need to order the following from IBM Cloud classic infrastructure:

  1. Endurance iSCSI block storage in the same datacenter as your hosts, with OS type VMware.
  2. A private portable subnet on the storage VLAN in your instance. Ensure the subnet is large enough to allocate two usable IP addresses for every current or future host in your cluster. We are ordering a single subnet for convenience, although it is possible to authorize multiple subnets (either for different hosts, or for different interfaces on each host). A single /25 subnet should be sufficient for any cluster since VMware vCenter Server (VCS) limits you to 59 hosts per cluster.

The Endurance authorization process authorizes each host individually to the storage, and assigns a unique iQN and CHAP credentials to each host. After authorizing the hosts, we then specify which subnet or subnets each host will be using to connect to the storage, so that the LUN accepts connections not only from the hosts’ primary IP addresses but also these alternate portable subnets. The following Python script issues the various API calls needed for these authorizations, assuming that we know the storage, subnet, and host ids:

STORAGE_ID = 157237344
SUBNET_ID = 2457318
HOST_IDS = (1605399, 1641947, 1468179)

# Connect to SoftLayer
client = SoftLayer.Client(username = USERNAME, api_key = API_KEY, endpoint_url = SoftLayer.API_PUBLIC_ENDPOINT)

# Authorize hosts to storage
for host_id in HOST_IDS :
  try :
    client['SoftLayer_Network_Storage_Iscsi'].allowAccessFromHost('SoftLayer_Hardware', host_id, id = STORAGE_ID)
  except :
    if 'Already Authorized' in sys.exc_info()[1].message :
      pass
    else :
      raise

# Lookup the "iSCSI ACL object id" for each host
hardwareMask = 'mask[allowedHardware[allowedHost[credential]]]'
result = client['SoftLayer_Network_Storage_Iscsi'].getObject(id = STORAGE_ID, mask = hardwareMask)
aclOids = [x['allowedHost']['id'] for x in result['allowedHardware']]

# Add our iSCSI subnet to each host's iSCSI ACL
for acl_id in aclOids :
  # Assign; note subnet is passed as array
  client['SoftLayer_Network_Storage_Allowed_Host'].assignSubnetsToAcl([SUBNET_ID], id = acl_id)

  # Verify success
  result = client['SoftLayer_Network_Storage_Allowed_Host'].getSubnetsInAcl(id = acl_id)
  assert len(result) > 0

At this point, the hosts are authorized to the storage. But before we can connect them to the storage we need to collect some additional information. First, we need to collect the iQN and CHAP credentials that were issued for the storage to each host:

STORAGE_ID = 157237344

# Connect to SoftLayer
client = SoftLayer.Client(username = USERNAME, api_key = API_KEY, endpoint_url = SoftLayer.API_PUBLIC_ENDPOINT)

# Lookup the iQN and credentials for each host
hardwareMask = 'mask[allowedHardware[allowedHost[credential]]]'
result = client['SoftLayer_Network_Storage_Iscsi'].getObject(id = STORAGE_ID, mask = hardwareMask)
creds = [ { 'host' : x['fullyQualifiedDomainName'],
            'iqn'  : x['allowedHost']['name'],
            'user' : x['allowedHost']['credential']['username'],
            'pass' : x['allowedHost']['credential']['password'] } for x in result['allowedHardware']]
print("Host connection details")
pprint.pprint(creds)

For example:

Host connection details
[{'host': 'host002.smoonen.example.com',
  'iqn': 'iqn.2020-07.com.ibm:ibm02su1368749-h1468179',
  'pass': 'dK3bACHQQSg5BPwA',
  'user': 'IBM02SU1368749-H1468179'},
 {'host': 'host001.smoonen.example.com',
  'iqn': 'iqn.2020-07.com.ibm:ibm02su1368749-h1641947',
  'pass': 'kFCw2TDLr5bL4Ex6',
  'user': 'IBM02SU1368749-H1641947'},
 {'host': 'host000.smoonen.example.com',
  'iqn': 'iqn.2020-07.com.ibm:ibm02su1368749-h1605399',
  'pass': 'reTLYrSe2ShPzZ6A',
  'user': 'IBM02SU1368749-H1605399'}]

Note that Endurance storage uses the same iQN and CHAP credentials for all LUNs authorized to a host. This will enable us to attach multiple LUNs using the same HBA.

Next, we need to retrieve the two IP addresses for the iSCSI LUN:

STORAGE_ID = 157237344

# Connect to SoftLayer
client = SoftLayer.Client(username = USERNAME, api_key = API_KEY, endpoint_url = SoftLayer.API_PUBLIC_ENDPOINT)

print("Target IP addresses")
storage = client['SoftLayer_Network_Storage_Iscsi'].getIscsiTargetIpAddresses(id = STORAGE_ID)
pprint.pprint(storage)

For example:

Target IP addresses
['161.26.114.170', '161.26.114.171']

Finally, we need to identify the vendor suffix on the LUN’s WWN so that we can positively identify it in vSphere. We can do this as follows:

STORAGE_ID = 157237344

# Connect to SoftLayer
client = SoftLayer.Client(username = USERNAME, api_key = API_KEY, endpoint_url = SoftLayer.API_PUBLIC_ENDPOINT)

props = client['SoftLayer_Network_Storage_Iscsi'].getProperties(id = STORAGE_ID)
try    : wwn = [x['value'] for x in props if len(x['value']) == 24 and x['value'].isalnum()][0]
except : raise Exception("No WWN")
print("WWN: %s" % wwn)

For example:

WWN: 38305659702b4f6f5a5a3044

Armed with this information, we can now attach the hosts to the storage.

First, create two new portgroups on your private vDS. Our design uses a shared vDS across clusters but unique portgroups, so they should be named based on the instance and cluster name, for example, smoonen-mgmt-iSCSI-A and smoonen-mgmt-iSCSI-B. Tag these port groups with the storage VLAN, and ensure that each portgroup has only one active uplink. iSCSI-A should have uplink1 active and uplink2 unused, while iSCSI-B should have uplink2 active and uplink1 unused:

Next, create kernel ports for all hosts in each port group, using up IP addresses from the subnet you ordered earlier. You will end up using two IP addresses for each host. Set the gateway to Configure on VMkernel adapters and using the gateway address for your subnet:

Next, let’s begin a PowerCLI session to connect to the storage and create the datastore. First, as a one-time setup, we must enable the software iSCSI adapter on every host:

PS /Users/smoonen/vmware> $myhost = Get-VMHost host000.smoonen.example.com
PS /Users/smoonen@us.ibm.com/Desktop> Get-VMHostStorage -VMHost $myhost | Set-VMHostStorage -SoftwareIScsiEnabled $True

SoftwareIScsiEnabled
--------------------
True

Next, also as a one-time setup on each host, bind the iSCSI kernel ports to the iSCSI adapter:

PS /Users/smoonen/vmware> $vmkA = Get-VMHostNetworkAdapter -PortGroup smoonen-mgmt-iSCSI-A -VMHost $myhost
PS /Users/smoonen/vmware> $vmkB = Get-VMHostNetworkAdapter -PortGroup smoonen-mgmt-iSCSI-B -VMHost $myhost
PS /Users/smoonen/vmware> $esxcli = Get-EsxCli -V2 -VMHost $myhost
PS /Users/smoonen/vmware> $esxcli.iscsi.networkportal.add.Invoke(@{adapter='vmhba64';force=$true;nic=$vmkA})
true
PS /Users/smoonen/vmware> $esxcli.iscsi.networkportal.add.Invoke(@{adapter='vmhba64';force=$true;nic=$vmkB})
true

Finally, once for each host, we set the host iQN to the value expected by IBM Cloud infrastructure, and also initialize the CHAP credentials:

PS /Users/smoonen/vmware> $esxcli.iscsi.adapter.set.Invoke(@{adapter='vmhba64'; name='iqn.2020-07.com.ibm:ibm02su1368749-h1605399'}) 
false
PS /Users/smoonen/vmware> $hba = Get-VMHostHba -VMHost $myhost -Device vmhba64
PS /Users/smoonen/vmware> Set-VMHostHba -IscsiHba $hba -MutualChapEnabled $false -ChapType Preferred -ChapName "IBM02SU1368749-H1605399" -ChapPassword "reTLYrSe2ShPzZ6A"

Device     Type         Model                          Status
------     ----         -----                          ------
vmhba64    IScsi        iSCSI Software Adapter         online

Now, for each LUN, on each host we must add that LUN’s target addresses (obtained above) as dynamic discovery targets. You should not assume that all LUNs created in the same datacenter share the same addresses:

PS /Users/smoonen/vmware> New-IScsiHbaTarget -IScsiHba $hba -Address "161.26.114.170"             

Address              Port  Type
-------              ----  ----
161.26.114.170       3260  Send

PS /Users/smoonen/vmware> New-IScsiHbaTarget -IScsiHba $hba -Address "161.26.114.171"

Address              Port  Type
-------              ----  ----
161.26.114.171       3260  Send

After this, we rescan on each host for available LUNs and datastores:

PS /Users/smoonen/vmware> Get-VMHostStorage -VMHost $myhost -RescanAllHba -RescanVmfs

SoftwareIScsiEnabled
--------------------
True

This enables us to locate the new LUN and create a VMFS datastore on it. We locate the LUN on all hosts but create the datastore on one host. Locate the LUN using the WWN suffix obtained above:

PS /Users/smoonen/vmware> $disks = Get-VMHostDisk -Id *38305659702b4f6f5a5a3044
PS /Users/smoonen/vmware> New-Datastore -VMHost $myhost -Vmfs -Name "smoonen-mgmt2" -Path $disks[0].ScsiLun.CanonicalName        

Name                               FreeSpaceGB      CapacityGB
----                               -----------      ----------
smoonen-mgmt2                           48.801          49.750

Finally, rescan on all hosts to discover the datastore:

PS /Users/smoonen/vmware> Get-VMHostStorage -VMHost $myhost -RescanAllHba -RescanVmfs

SoftwareIScsiEnabled
--------------------
True

We can confirm that we have multiple paths to the LUN as follows:

PS /Users/smoonen/vmware> $luns = Get-ScsiLun -Id *38305659702b4f6f5a5a3044
PS /Users/smoonen/vmware> Get-ScsiLunPath -ScsiLun $luns[0]

Name       SanID                                    State      Preferred
----       -----                                    -----      ---------
vmhba64:C… iqn.1992-08.com.netapp:stfdal1303        Standby    False
vmhba64:C… iqn.1992-08.com.netapp:stfdal1303        Standby    False
vmhba64:C… iqn.1992-08.com.netapp:stfdal1303        Active     False
vmhba64:C… iqn.1992-08.com.netapp:stfdal1303        Active     False

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