VMFS Block Sizes - does it affect files within disks?

[dgwharrison]

Hi all,

I know that if we choose a larger block size we can have a larger total disk (up to 2TB i think). I also know that if i choose a larger block size, say 8mb, then even the small files on my vmfs will take up to that 8mb of disk space. My question is what about small files within vm disks such as a windows vm running ntfs. Are the files on that guest going to take the large block size of 8mb regarless of their size?

[vmroyale]

Hello.

Check out this post (and especially the comments from Satyam Vaghani) over at Duncan's site. It will answer all of your questions.

[pigbloke]

The VMFS block size will only apply to the files on your VMFS datastore (vmdk, vmx, log files etc). Files within your vmdk file will conform to the block size of the guest file system. If your guest is thin provisioned, the vmdk file will grow in increments of your VMFS block size.

Hope this helps.

Nick

[RParker · Accepted solution]

say 8mb, then even the small files on my vmfs will take up to that 8mb of disk space

No there is a sub layer that takes into account smaller files, files of LESS than the pre determined threshold (I can't remember exactly what it is) are not part of that minimum block size. So small files are 1/64 of the block size. With 8 Meg block size they are 1/256 size of the block size.

So I had the same issue wondering about log files and such, and the VMFS takes this into account so you don't waste the space.

[RParker]

If your guest is thin provisioned, the vmdk file will grow in increments of your VMFS block size.

He is asking if files like logs for instance, if they are 1k or less, they will occupy whatever the block size is, but that doesn't count. Files of less than (X) size are considered to be 1/64 of the block size, and therefore are not counted against the quota, and can actually be smaller than the block size without occupying 8meg or 4 meg whatever the block size is...

The growing in block size is different.