Dell Compellent SCv3020 - Space / Storage confusion

Hi All, 

New to the board so please forgive any newbieness about this post.

I've basically inherited looking after an already existing Compellent that had some space issues, new disks had been added to try and resolve that issue, but this was quickly eaten up by 'something' before we had the chance to look at anything in more detail.

Very Brief rundown, there was originally 10 x 900Gb SAS drives and errors were appearing in the logs advising that the storage was about to run out of space within 30 days, so the quick fire solution was to stick in another 5 x 900Gb drives, but we don't appear to have had much benefit of this.

All of the disks appeared to be added to the assigned folder, which looks like it has been configured as dual redundancy.

We have 3 volumes created that are presented as datastores to vmware, these are 1Tb, 2Tb and 3Tb.

Below are some screenshots of the DSM highlighting summary, alerts, disks, storage, snapshots etc.

I'm struggling to try and understand where all the space is being used, has it been configured correctly in the first instance, how can it be changed to single redundancy (assuming that's better) and is there enough space to even achieve that?

Here is the current summary

 

Here is the current alerts (after installing an additional 5 x 900Gb Disks)

Here is storage types

Here is the Tier 1 Storage

Here is the Volumes

Finally here are snapshots on 2 of the volumes

I would appreciate if anyone can assist to see what is wrong, and i assume that there are probably lots needing done, but i don't know where to even start here. Are snapshots even required on the Compellent, if we take snapshots of the VM's from within VMware? Or are these a different type of snapshot.

I appreciate that this is a large post, that probably doesn't have all of the relevant information for anyone to make informed suggestions, but if you can let mw know what 'other' type of information may be required, i'd appreciate it.

Thanks in advance.