Fixing Mac OS X Time Machine network errors on HP MediaSmart Servers

I recently got an HP ex490 MediaSmart home server to replace my burnt out Acer h340 EasyStore machine. The ex490 is a nice enough machine, and upgrading the CPU to make it as good or better than the ex495 is an easy task, but the main reason I went for the mediasmart server was Mac support.

I live in an OS agnostic house, and the ability to back up Mac OS X via Time Machine along with the PC was a definite selling point.
But something happened on the way from concept to delivery. The HP home server is fairly well integrated with the Mac (it includes a handy media collector program that grabs photos, music and movie files from your computers to your home server) but I couldn’t get the time machine to function properly.

I kept getting network errors when I’d go to create my time machine backup disc via the preferences pane. It would always fail partway through. Now to be fair, my MacBook Pro is not standard – it’s got an internal raid and I was trying to create a 1.2 terabyte time capsule, but a quick web search showed that I certainly wasn’t the only person having this problem. Many people cant create a Time Machine disk bigger than 75 gigs. Many are reporting problems with the Time Machine function in the most recent version of the HP mediasmart software.
If you’re having this problem, here’s what worked for me.

WARNING: The following steps involve editing the registry on your server. You can mess things up if you do it wrong.
Time Machine seems to have a problem with the IRP stack size default on the Windows Home Server. Fixing it is relatively simple, though not without risk (you did read that warning above right?). Make sure your media smart software is up to date and reboot both your server and your Mac to see if that fixes the problem before you try the following.

First you’ll need desktop access to your server, this can be done with an external mouse and keyboard, but the easiest way is with an add-in. If you have Advance Admin Console installed you can use it’s built in show desktop feature, or if you want a basic add-in try To Desktop. Either of these will give you easy access to the server desktop from the console.
[GARD]
Once you’ve got desktop access you can do the following steps. These are from this Microsoft technical bulletin, with the addition of the specific number I used to get my system to work properly:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesLanmanServerParameters
3. Click Edit, point to New, and then click DWORD Value.
4. Type IRPStackSize, and then press ENTER to name the value.
Note Type IRPStackSize exactly as it is displayed. The value name is case sensitive.
5. Click Edit, and then click Modify.
6. In the Data Value box, type the value that is appropriate for the network.

The value I used was 27 decimal. Type in 27 in the data box and click the button for decimal. Then click OK Close the registry editor and reboot the server. Then try to set up your Time Machine disk in the OS X media smart preferences panel again. Hopefully it’s now working for you like it is for me!