Recently had a problem were Veeam was giving bother on
one VM that had a dedicated datastore, not allowing
hot-add virtual appliance mode to work.
I originally thought it was a problem with CBT (changed block tracking) so I disabled that, with no luck, as it transpires there were a few (all datastore formatting related) problems:
Veeam proxy‘s datastore was formatted in
VFMS-3with a 2MB
block sizeand upgraded to
VMFS-5(retaining its 2MB
block sizeof course – otherwise a reformat would be needed).
source machine‘s datastore was formatted in
VMFS-3with an 8MB
block sizeand later upgraded to
VMFS-5(retaining its 8MB
- The target datastore was formatted in
VMFS-5natively with a unified 1MB
So when the
proxy tries to
hot-add the disk the
VMFS block size on the
source machine‘s datastore is larger than the
block size and the
One solution was to put it in network mode but this can be slow and it’s not a nice way of doing things, so I wanted to run it in VA mode.
What I ended up doing was shutting down the
source machine, migrating it to a
VMFS-5 datastore, reformatting it’s
original datastore to native
VMFS-5 volumes are all created with a unified 1MB
block size) and migrating the
source VM back to its
hot-add then worked as expected. In an ideal world one would reformat all their datastores to
VMFS-5 with the standard 1MB
block size and this is what I am working towards.
“What about the VMDK file size limit tied to
block size?” I hear you say – well, as of
VMFS-5 the 1MB
block size now supports 2TB .vmdk files:
The limits that apply to VMFS-5 datastores are:
The maximum virtual disk (VMDK) size is 2 TB minus 512 B. The maximum
virtual-mode RDM size is 2 TB minus 512 B. Physical-mode RDMs are
supported up to 64 TB.
As of VSphere 5.5 this will change to 64TB – though why you would want a .vmdk this size beats me – i’d have the disk split and clustered, if it was a Windows box e.g. SBS, Exchange or SQL – though, if you need this disk size you’re likely already using
RDM for those.
Any input on this however is welcome.
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