Storage - iSCSI, VSA, Fibre Channel, Storage Profiles, Storage I/O Control
VMFS-5 unified block size is 1 MB and the maximum file size is 2 TB.
VMFS-5 supports LUNs greater than 2 TB.
GUID Partition Table (GPT) is used for VMFS-5
64 TB is the maximum LUN size.
LUNs should be presented with the same ID for each host.
Best practices for zoning suggest a single initiator/single target zoning method.
vStorage APIs for Array Integration (VAAI) can be realized when cloning a VM, when deploying a VM from a template, or when performing a storage vMotion with in an array.
VAAI space reclamation feature does not reclaim space when data is deleted by the guest OS.
Storage vMotion is not supported on VM protected by FT.
The vSphere Storage Appliance (VSA) converts local disk storage into shared NFS storage.
The VSA manager is installed on the server running vCenter.
The VSA state can be identified as Online, Offline, or degraded.
The VSA is considered “Degraded” when high availability is lost because a replica has come online as a primary.
Storage Profile ensure VMs are placed on storage devices that can guarantee capacity, performance, availability, and redundancy.
Storage Profiles can be defined manually by an Administrator or automatically with the vSphere APIs for Storage Awareness (VASA)
When a path fails storage I/O may pause for 30-60 seconds until the host has determined the link failed and completes the fail over process.
All Paths Down (APD) refers to a situation in which all paths to a storage device are lost.
An RDM that requires capacity greater than 2 TB must be created in physical compatibility mode.
RDM with NPIV allows a VM to be assigned a WWN that can be managed and monitored as it accesses the storage array.
A VM enabled for NPIV based RDM can only be migrated with vMotion if the mapping files are stored on the same datastore as the VM config file.
Components of VMwares Pluggable Storage Architecture (PSA)
- SATP - Storage Array Type Plugin
- NMP - Native Multipathing Plugin
- MPP - Multipathing Plugin
- PSP - Path Selection Plugins
Native multipathing policies in vSphere 5:
- MRU - Most Recently Used
- Round Robin
MRU provides fail over but not fail back.
In order to set a preferred path the multipathing policy should be set to Fixed.
The Round Robin multipathing policy provides load balancing over all paths to the datastore.
iSCSI storage should use a dedicated, isolated, non-routed network.
iSCSI uses TCP port 3260 by default.
iSCSI discovery methods available in vSphere 5 include Send Targets and Static Discovery.
Software iSCS and Dependent Hardware iSCSI require a VMkernel port.
Storage I/O control is initiated when the congestion threshold is exceeded.
The default Storage I/O control congestion threshold is 30ms.
The congestion threshold can be configured between 10 - 100ms.
All datastores that share spindles on the array must have the same congestion threshold for Storage I/O control to work correctly.
Storage I/O control is supported on Fiber Channel, iSCSI, and NFS connected storage.
IOPS requirement = (Total IOPS * %reads) + (Total IOPS * %writes * RAID Penalty)
RAID Penalty: RAID 0 = 0, RAID 1 = 2, RAID 5 = 4, RAID 1+0 (or RAID 10) = 2
IOPS required = Throughput / workload
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