SQL 2012 :: Piecemeal Restore With Filestream Database?

We have one database with Filestream enabled. There is one table "dbo.files" which uses Filestream.

We created a filestream filegroup Filegroup1 and added 3 data containers to it. (3 filestream data containers within the same filegroup.)

We have three LUNs F:, G:, H: each with a capacity of 2TB (That is the limitation). F: and G: are almost full. So, I restricted their growth so inserts do not happen into these data containers. Inserts are now going into H: drive which has lots of free space. Our application code prevents any sort of deletes or updates to this table. So data in the growth restricted containers will never change.

Now the database is around 6 TB in size and backups is a challenge. We are contemplating on migrating storage to netAPP and use their snapmanager console which is much faster.

However, until then, we need a solution with native SQL backups. We tried partial backups and piecemeal restore.

WE tried this on a test server :

1) Partial backup only the read-only data containers first, (F: and G:) (The plan is to back these up just once a month as this data never changes).

2) Partial backup the primary filegroup plus the third data container in the Filestream filegroup which is subject to inserts (H:)

While restoring, we tried the online restore, First, I restored the backup obtained from step 2 above with recovery option. Then I restored the backup obtained from step 1 with recovery. I see that the database was brought online. However, when I try to query the dbo.files table, I get an error stating that some files of the filestream filegroup are offline.