I am pretty sure the lrdat file cannot be used to restore your catalog. The lrdat file only contains all the previews and has no info on develop settings or anything like that. It sounds like your best hope is to try to recover the lrcat files. Perhaps also look on your backup disk if your backup perhaps contains any of the automatic backups that Lightroom itself makes.
Aww, shucks. I figured as much but was hoping I was wrong. Unfortunately it seems all the backups are on the dead drive and none of them made it to my backup NAS. I remember changing my backup routine because of other problems sometime, I guess 2013, and it seems I didn't check to make sure everything was working properly. Oh well, lesson learned. Currently running several recovery software, so far not much luck.
I am new to forum + Lr but so far this is what I read about NAS drives with Lr:
From "The Adobe Photoshop Lightroom CC/Lightroom 6 Book" it states: "The Lightroom files can be imported to any drive destination you like. The only restriction you have is that the catalog file cannot be stored on a network attached storage (NAS) device. This is because the Lightroom Catalog can't be shared with other users across a network and is an intentional SQLite database limitation designed to avoid corruption." (pg. 50)
So any Lr catalogs stored on a NAS drive would be VERY problematic:(
I am researching this as we were going to use our NAS drive as our backup and WAS going to use it for our Lr catalog storage = I am regrouping after reading NAS drives aren't for Lr catalogs:( Now I must go buy new harddrives to hold the catalogs as no room on laptop for catalogs....hoping to use NAS for Lr photo storage at least).
The book I quoted from just came out in May 2015 so info very current. Sorry to deliver the sad news:( It is a very good book tho!
You might want to also check out this post on: Which Lightroom files do I need to back up? http://www.lightroomqueen.com/backup-lightroom-files/#comments (Scroll down the comments as are some 2015 comments too!)
And her post on: Disaster strikes – a corrupted catalog! http://www.lightroomqueen.com/disaster-strikes-corrupted-catalog/
(Scroll down the comments as are some 2015 comments too!)
Now I am trying to figure out which hard drive to get to backup the Lr catalogs?? The Most (and Least) Reliable Hard Drive Brands: http://lifehacker.com/the-most-and-least-reliable-hard-drive-brands-1505797966.
Not sure which kind of hard drive you had that crashed?? Any ones you would recommend going forward?