How VMFS Block Size Varies

Here you will find out:

what is VMFS block size

how VMFS block size varies

how DiskInternals can help you

Are you ready? Let's read!

VMFS block size and limitations

When creating a VMFS volume for an ESX Server, the user must pay great attention to the file system’s block size. This affects what the maximum size of the virtual disk file can be, which then will be very difficult to change in any way without the data disappearing.

For VMFS 2 and VMFS 3, a small block size reduces the useful space for file fragmentation. Therefore, it is the 1 MB block size that is more preferable for building volumes. But this does not mean that you cannot use other dimensions as you wish.

The main limits and preferences for block sizes and the corresponding file sizes in VMFS 2 and 3, of course, are there and you should know them:

For VMFS 2:

1 MB - 456 GB

2 MB - 912 GB

4 MB - 1.78 TB

8, 16, 32, 64 MB - 2 TB

For VMFS 3:

1 MB - 256 GB

2 MB - 512 GB

4 MB - 1024 GB

8 MB - 1488 GB

16, 32, 64 MB - Invalid block size

For VMFS 5: The newly created VMFS 5 datastores use one miniature block size of 1 MB.

For VMFS 6: This type of volume creation introduces two new block sizes: a small file block (SFB) and a large file block (LFB).

The SFB can vary from 64 KB to 1 MB for future use cases, but more often 1 MB is used. The LFB size corresponds to 512 MB.

How to choose block size for VMware VMFS

Based on the experience and knowledge of many users, using different block sizes for different data storage devices can be harmful, as can happen when you have a large enough storage medium, but VMDK is limited by the size of the block.

Therefore, it is most reasonable to choose the maximum VMFS block size, regardless of the size of the data store.

VMware VMFS block size: used space

The file block size is dependent on the size of your block. Thus, free space is not consumed quickly even if you have programmed a large block.

VMware VMFS block size: performance

Previous experience also tells us that the size of the block does not significantly affect the performance of virtual disks. But still, make a smart choice, and follow the recommendations described above.

How can VMFS recovery be performed?

There is a special, professional tool for this: DiskInternals VMFS Recovery.

This utility has been used for many years and automatically checks the current status of volumes, VMware VMFS data storages, and disks, as well as reads images in VMware vSphere, ESXi/ESX Servers, and VMFS structures where possible.

All information is restored online without shutting down the system. You will get a preview of the data found, which is necessary to verify that the program works and to give you peace of mind. If the results satisfy you, then purchase a license. Next, simply export the data to the desired storage location. At all stages of the process, you will be assisted by the Recovery Wizard, so there is no reason for concern!