OSDOCS-14322# Add hyperdisk limits for C3/N4

Author: Lisa Pettyjohn

modules/persistent-storage-csi-gcp-hyperdisk-limitations.adoc

@@ -7,6 +7,8 @@
 = C3 and N4 instance type limitations
 The GCP PD CSI driver support for the C3 instance type for bare metal and N4 machine series have the following limitations:
 
+* The minimum volume size for hyperdisk-balanced disks is 4Gi. Creating disks with a smaller size is not supported. Also, {product-title} does not round up to the minimum size. You must set the correct sizing yourself.
+
 * Cloning volumes is not supported when using storage pools.
 
 * For cloning or resizing, hyperdisk-balanced disks original volume size must be 6Gi or greater.
@@ -22,4 +24,6 @@ For information about creating the storage class, see Step 2 in Section _Setting
 
 * Clusters with mixed virtual machines (VMs) that use different storage types, for example, N2 and N4, are not supported. This is due to hyperdisks-balanced disks not being usable on most legacy VMs. Similarly, regular persistent disks are not usable on N4/C3 VMs.
 
-* A GCP cluster with c3-standard-2, c3-standard-4, n4-standard-2, and n4-standard-4 nodes can erroneously exceed the maximum attachable disk number, which should be 16 (link:https://issues.redhat.com/browse/OCPBUGS-39258[JIRA link]).
+* A GCP cluster with c3-standard-2, c3-standard-4, n4-standard-2, and n4-standard-4 nodes can erroneously exceed the maximum attachable disk number, which should be 16 (link:https://issues.redhat.com/browse/OCPBUGS-39258[JIRA link]).
+
+* link:https://cloud.google.com/compute/docs/disks/hyperdisks#limitations[Additional limitations].

modules/storage-persistent-storage-pv.adoc

@@ -165,7 +165,7 @@ ifdef::openshift-enterprise,openshift-webscale,openshift-origin[]
 |Fibre Channel  | ✅ | ✅ |✅ |  ✅ ^[3]^
 endif::[]
 ifndef::openshift-rosa[]
-|GCP Persistent Disk  | ✅ |✅ |   |   
+|GCP Persistent Disk  | ✅ |✅ | ✅ ^[4]^ | ✅ ^[4]^
 |GCP Filestore | ✅ | ✅ |✅ | ✅
 endif::openshift-rosa[]
 ifdef::openshift-enterprise,openshift-webscale,openshift-origin[]
@@ -181,7 +181,7 @@ ifdef::openshift-enterprise,openshift-webscale,openshift-origin[]
 |NFS  | ✅ | ✅ |✅ | ✅
 |OpenStack Manila  |  |✅ |  | ✅
 |{rh-storage-first}  | ✅ |✅ |  | ✅
-|VMware vSphere | ✅ |✅ |  |  ✅ ^[4]^
+|VMware vSphere | ✅ |✅ |  |  ✅ ^[5]^
 endif::[]
 |===
 [.small]
@@ -193,7 +193,22 @@ endif::[]
 3. Only raw block volumes support the ReadWriteMany (RWX) access mode for Fibre Channel and iSCSI. For more information, see "Block volume support".
 
 ifndef::openshift-dedicated,openshift-rosa[]
-4. If the underlying vSphere environment supports the vSAN file service, then the vSphere Container Storage Interface (CSI) Driver Operator installed by
+
+4. For GCP hyperdisk-balanced disks:
+
+* ReadOnlyMany is _not_ supported.
+
+* ReadWriteMany is supported.
+
+* Cloning and snapshotting is disabled for disks with ReadWriteMany enabled.
+
+* You can attach a single hyperdisk-balanced disk volume in multi-writer mode to a maximum of 8 instances.
+
+* You cannot resize a disk in multi-writer mode unless you detach the disk from all instances.
+
+* https://cloud.google.com/compute/docs/disks/attach-disks[Additional limitations].
+
+5. If the underlying vSphere environment supports the vSAN file service, then the vSphere Container Storage Interface (CSI) Driver Operator installed by
 {product-title} supports provisioning of ReadWriteMany (RWX) volumes. If you do not have vSAN file service configured, and you request RWX, the volume fails to get created and an error is logged. For more information, see "Using Container Storage Interface" -> "VMware vSphere CSI Driver Operator".
 endif::openshift-dedicated,openshift-rosa[]
 // GCE Persistent Disks, or Openstack Cinder PVs.