Importing an old Plone 3.3 site as second site in my Plone 4.1 - upgrade

Question

I'm running a Plone 4.1 site, and since we have a second site that has been down for a while, and which was built over Plone 3.3, we'd like to import that site as well into our Plone 4.1.
I have already created a separate mount point, but copying the old Data.fs file into the new mount point didn't really work.
What I'd like to do is: grab the Data.fs from the old plone install, move it to a separate mount point (it will be placed in a subfolder now, it was just under var/filestorage before), and port it to v.4.1 in some way.
I've searched various tutorials but didn't find any relevant hint on how to solve this need, anybody could give me some pointers?
thanks!

Answer 1

I'd suggest to:
create a clean plone4 separated environment.
copy the old data.fs to the new env
follow the section "Updating a custom Plone 3 buildout for Plone 4" from the Plone Upgrade Guide
export your upgraded site and import it in your first environment

Answer 2

Thanks a lot Giacomo, i was able to move further through the approach you suggested.
So what I've done was:
create a vanilla test instance matching the target version (4.1)
copy Data.fs and blobstorage folder from the old site to my test instance. (In the meantime I realised the old site was a 4.0, not a 3.3, hence I moved also the whole blobstorage folder, otherwise further export wouldn't have worked).
startup my test instance, and upgrade the storage through the "Upgrade" button on plone startup page
from ZMI, export my site to a zexp file
upload the zexp file into zinstance/var/instance/import on the target platform
enter the ZMI of the target platform, select the folder that i mapped to the mount point for my second site, and there import the zexp file
This last step of importing the zexp fails with the following error:
Error Type: TypeError
Error Value: Blobs are not supported
Troubleshooting Suggestions
The URL may be incorrect.
The parameters passed to this resource may be incorrect.
A resource that this resource relies on may be encountering an error.
Which in the logs corresponds to:
2011-10-05T12:49:27 ERROR Zope.SiteErrorLog 1317811767.860.405425857164 http://localhost:8080/mysecondsite/manage_importObject
Traceback (innermost last):
Module ZPublisher.Publish, line 126, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 46, in call_object
Module OFS.ObjectManager, line 619, in manage_importObject
Module OFS.ObjectManager, line 637, in _importObjectFromFile
Module ZODB.ExportImport, line 92, in importFile
Module transaction._transaction, line 260, in savepoint
Module transaction._transaction, line 257, in savepoint
Module transaction._transaction, line 690, in __init__
Module ZODB.Connection, line 1123, in savepoint
Module ZODB.Connection, line 587, in _commit
Module ZODB.ExportImport, line 181, in _importDuringCommit
Module ZODB.Connection, line 1302, in storeBlob
Module ZODB.Connection, line 1331, in _getBlobPath
Module ZODB.Connection, line 1344, in temporaryDirectory
Module ZODB.blob, line 686, in temporaryDirectory
Module ZODB.blob, line 492, in temp_dir
TypeError: Blobs are not supported
Any clue of how to solve this one?
Thanks!
silvio