EX4100 My Cloud Time Machine Compliance

I have been using NAS devices from another manufacturer for about four years but a couple of years ago, along with other users, I started getting errors every few months which I have also found reported on here; i.e.:

‘Time Machine completed a verification of your backups on “NAS Device”. To improve reliability, Time Machine must create a new backup for you.’

I am now looking to buy another NAS and I have my eye on the EX4100 as it has all the connectivity and features I need with the option of expansion. However, I am not convinced that My Cloud is going to be any more compatible than my last NAS OS especially as none of the several threads I have read seem to have been resolved conclusively.

I read on the Apple Discussion Forums on this topic that no third party NAS system is Time Machine compliant and links to this article in the Mac Developer Library:


It concerns me that manufacturers may be advertising their products as being Time Machine compatible when in fact they may not be.

As anybody who has experience this problem will know, it may not happen for some time after the establishment of an initial Time Machine backup by which time many suppliers’ refunds policy has expired and the only option would be a like for like replacement.

Can anybody, preferably a member of WD staff, please advise me whether the EX4100 and My Cloud OS are now Time Machine compliant as per the linked Apple requirements?


All My Cloud support Time Machine from scratch, it’s a built-in feature of the My Cloud Operating System. Therefore you have AFP protocol support that needs to be enabled (by default it is ON) and the Tiem Machine environment that needs to be enabled. Having these both ON, activate your Time Machine software and use the My Cloud device as target disk for the Time Machine backup.

BUT: Time Machine process may last very long in the first run. This behaviour is bound to the way, Time Machine is operating. It can be seen as a block based data but using file based transfer. This leads to the fact, that the first full backup may last “ages” until it is finished. This cannot be speed up as it is caused by this block-based-file-based behaviour.

Some screenshots attached for better explanation, Web Interface Settings -> General, Block Mac Backups:

Click on “Configure” opens a dialogue, a) in which folder the Backups shall be stored (TimeMachineBackup by Default)

and what amount of the overall capacity the backups can be used:

If you have My Cloud Mirror device and above, within Settings -> Network, there is the trigger for AFP Apple File Protocol, by default ON

If you have My Cloud device, the white Single Bay My Cloud, there is no trigger for AFP, here it’s always ON:

The default share TimeMachineBackup has limited settings but you can disable “Public” property if you want to use user based authentication:

Similar to this, here is the folder settings page for the Single Bay My Cloud device:

Hello Joerg_A,

Thank you very much for your detailed reply.

However, I had found all that information before I posted my question which it doesn’t really answer, I’m afraid.

Most NAS systems state that they are Time Machine compatible and having had two previously, I know that the first backup takes a long time; 500GB of data takes two days via Ethernet or about a week over Wifi. I can appreciate that the My Cloud system is easier to set up but my question relates not to how to set up Time Machine but what happens several weeks or, as has been my experience on another system, several months later when the quoted error (exemplified by the image below which I found online) appears and the only option offered is to start a new backup (as I keep/kept my NAS in a different room to where I use my Mac by necessity, this was a major inconvenience.

Now that I have the opportunity to replace the NAS, I was looking to find a system which did not present these problems and in doing so, I found that the cause of the problem was attributed to third party devices’ non-compliance to the criteria set out in the document I linked to and again below:


I won’t pretend I understand much of what it says but my theory is that NASs which aren’t compliant are not allowing Time Machine to delete old backups; hence it runs smoothly until the sparsebundle is full and then runs into difficulties which require a new backup to be started.

Having searched the WD community forums, I have found that this issue has been experienced by quite a few My Cloud users with one lengthy thread in particular. I really want to avoid this problem and was seeking information which would assure me that WD My Cloud products were Time Machine compliant or, if not, are WD aware of the problem and intend to make the products fully Time Machine compliant?


We have several, even hardcore Mac users in our teams and nobody yet has claimed what you described in the second quote. If the sparsebundle capacity is adjusted to a given amount, then our Mac (we are using for demos) is satring do delete the oldest backups to get space for the latest ones. My two cents…

Hello Joerg_A,

I think I admitted in my last message that it was an uninformed theory. Perhaps there is another explanation why the backups fail regularly after several weeks or months but it is still an issue experienced by many NAS users including WD My Cloud users. Having experienced it myself to the point of exasperation and that I am looking to replace my NAS with one which doesn’t do this. I am merely making enquiries before making a purchase but I am not reading anything which is very reassuring.

And whilst I accept that a bench Mac doesn’t have these problems, possibly because they do not have real world volumes of data change, this thread, with 109 posts shows that it affects WD customers:

Whilst it might be argued that the last post on that lengthy thread was a year ago, the most recent thread on this subject was in July this year:

There appears to be a ‘fix’ but everyday users ought not be expected to delve into using Terminal and SSH.

Incidentally, I felt I ought to add that since this problem started to get repetitive, I have kept a secondary USB Time Machine backup as a safety net. It has been going for about two years without this problem arising once.