vSphere 5 – Storage pt.1 VMFS and Provisioning
VMware® vStorage Virtual Machine File System (VMFS) is a high-performance cluster file system that provides storage virtualization optimized for virtual machines. Each virtual machine is encapsulated in a small set of files and VMFS is the default storage system for these files on physical SCSI disks and partitions. This File system enables the use of VMware® cluster features of DRS, High-Availability, and other storage enhancements.
For more information please see the following document here and the following KB here.
There are two ways to upgrade the VMFS to version 5 from previous 3.xx. An important for when upgrading VMFS-5 or provisioning new VMFS-5 is that legacy ESX host will not be able to see the new VMFS partitions. This is because of the enhancements made into ESX and the partitioning. Upgrading VMFS-5 is irreversible and consider always what you are doing. Lastly, there are many ways to provision VMFS-5 these are just two of the more common ways of doing it.
Method 1: Online Upgrade
Although an online upgrade does give you some of the new features in VMFS-5 it does not give you all of them. However, it is the least impacting and can be performed at anytime without an outage. Below are the features you will not gain by doing an in-place upgrade:
- VMFS-5 upgraded from VMFS-3 continues to use the previous file block size which may be larger than the unified 1MB file block size.
- VMFS-5 upgraded from VMFS-3 continues to use 64KB sub-blocks and not new 8K sub-blocks.
- VMFS-5 upgraded from VMFS-3 continues to have a file limit of 30720 rather than new file limit of > 100000 for newly created VMFS-5.
- VMFS-5 upgraded from VMFS-3 continues to use MBR (Master Boot Record) partition type; when the VMFS-5 volume is grown above 2TB, it automatically & seamlessly switches from MBR to GPT (GUID Partition Table) with no impact to the running VMs.
- VMFS-5 upgraded from VMFS-3 continue to have its partition starting on sector 128; newly created VMFS5 partitions will have their partition starting at sector 2048.
RDM – Raw Device Mappings
- There is now support for passthru RDMs to be ~ 60TB in size.
- Non-passthru RDMs are still limited to 2TB – 512 bytes.
- Both upgraded VMFS-5 & newly created VMFS-5 support the larger passthru RDM.
The end result in using the in place upgrade can be the following:
- Performance is not optimal
- non-standards can still be in place
- Disk Alignment will be a consistent issue with older environments
- File limit can be impacting in some cases
Method 1: How to perform an “Online” upgrade for VMFS-5
Upgrading a VMFS-3 to a VMFS-5 file system is a single-click operation. Once you have upgraded the host to VMware ESXi™ 5.0, go to the Configuration tab > Storage view. Select the VMFS-3 datastore, and above the Datastore Details window, an option Upgrade to VMFS-5 will be displayed:
Figure 3. Upgrade to VMFS-5
The upgrade process is online and non-disruptive. Virtual machines can continue to run on the VMFS-3 datastore while it is being upgraded. Upgrading the VMFS file system version is a one-way operation. There is no option to reverse the upgrade once it is executed. Additionally, once a file system has been upgraded, it will no longer be accessible by older ESX/ESXi 4.x hosts, so you need to ensure that all hosts accessing the datastore are running ESXi 5.0. In fact, there are checks built into vSphere which will prevent you from upgrading to VMFS-5 if any of the hosts accessing the datastore are running a version of ESX/ESXi that is older than 5.0.
As with any upgrade, VMware recommends that a backup of your file system is made prior to upgrading your VMFS-3 file system to VMFS-5.
Once the VMFS-5 volume is in place, the size can be extended to 64TB, even if it is a single extent, and ~2TB Virtual Machine Disks (VMDKs) can be created, no matter what the underlying file-block size is. These features are available ‘out of the box’ without any additional configuration steps.
NOTE: Some documentation are excerpts and provided and used from VMware Documentation and Sources..
Method 2: Provisioning New VMFS-5
This method explains how to update VMFS without performing an “online” upgrade. Essentially this would be the normal process of provisioning a VMFS LUN for ESXi 5 or older. Here are the listed benefits of VMFS-5 provisioning without doing an “online” upgrade.
- VMFS-5 has improved scalability and performance.
- VMFS-5 does not use SCSI-2 Reservations, but uses the ATS VAAI primitives.
- VMFS-5 uses GPT (GUID Partition Table) rather than MBR, which allows for pass-through RDM files greater than 2TB.
- Newly created VMFS-5 datastores use a single block size of 1MB.
- VMFS-5 has support for very small files (<1KB) by storing them in the metadata rather than in the file blocks.
- VMFS-5 uses sub-blocks of 8K rather than 64K, which reduces the space used by small files.
- VMFS-5 uses SCSI_READ16 and SCSI_WRITE16 cmds for I/O (VMFS-3 used SCSI_READ10 and SCSI_WRITE10 cmds for I/O).
- Disk Alignment for Guest OS’s become transparent and have less impact.
- Performance I/O and scalability become a greater value to running online vs. new.
As you can see the normal provisioning of VMFS-5 is a lot more robust in features and offers a great deal of improvement to just performing an “Online” upgrade. The online upgrade is easy and seamless but for normal considerations all benefits should be considered. In my case the chosen Method would be Method 2. The only instance in which an “Online” upgrade would be considered under normal circumstances would be if you were already at capacity on an existing array. In this type of scenario it could be viewed as a more beneficial way. Also, if you did not have Storage vMotion licensed through VMware further considerations on how to migrate to the new VMFS would have to be made. Migrating workloads to new VMFS-5 would be a bit more of a challenge in that case as well. However this is not an issue under most circumstances.
Method 2: How To provision new VMFS-5 for ESXi
- Connect to vSphere vCenter with vSphere Client
- Highlight a host and click the “Configuration” tab in the right pane.
- Click on “Storage”
- In the right pane click “Add Storage” (See image)
- Select the LUN you wish to add
- Expand the Name column to record the last four digits (this will be on the naa name) In this case it will be 0039. Click “Next”
- Select to use “VMFS-5″ option
- Current Disk Layout – Click “Next”
- Name the datastore using abbreviations for the customers name with the type of storage followed by the LUN LDEV (Yes, a standard). This example would be “Cust-Name”=name “SAN”=type “01″= Datastore Number “LDEV” = 0038. (cus-nam-san-01-1234)
- Select the radio button “Maximum available space” click > Next
- Click Finish and watch for the “task” to complete on the bottom of vSphere client
- After the task completes go to the Home > Inventory > Datastores
- Make sure there is a Fiber Storage folder created. Under that folder create a tenant folder and relocate the datastores in the new tenant name folder.
- After moving the folder you may need to provision this datastore for vCloud. Proceed to the optional method for this below.
Note: Some of the information contained in this blog post is provided by VMware Articles and on their website http://www.vmware.com