Should I split VMware virtual disk into multiple files or not?

There seems little point in splitting an image file unless you're creating it on a FAT32 volume or network share that has file size restrictions.

VMware has this to say:

Select Split virtual disk into multiple files if the virtual disk is stored on a file system that has a file size limitation.

Another reference has this to say:

Choosing to split VMDK into 2GB files has quite no impact on performance.

Anyway, the largest disk image file I've currently got (on my NTFS-formatted portable USB hard drive) is ~150GB. I've even backed it up using 7-zip to a network share overnight. No problems at all.

Performance-wise, seriously, for what you're doing you simply won't notice the difference between single and split images. I imagine a perceivable difference would start to appear with images into the 100s of GB in size. Still, if you want to go with what is technically the most performant, then that's a single monolithic image file which is what you're doing already. You're all good ;-)

Disadvantages of monolithic disks:

• If you delete snapshots and need to consolidate unused .vmdk files, if you need to defragment .vmdk files, etc., then your host needs as much free space as the entire .vmdk file. In contrast, if you use split disks, then your host needs only as much free space as one of the individual .vmdk extents.
• If you want to copy or back up a VM, you might be copying it to a file system that doesn't support such large files.
• If you're in the middle of copying or backing up a VM but need to cancel the operation and to resume it later, using split disks is much less painful.

Advantages of monolithic disks:

• Less file system clutter (and in that sense it's easier to manage).
• The VM will require fewer open file handles. Some host operating systems have a somewhat low limit on the maximum number of open file handles, and this can matter if you take a lot of snapshots.