Comparing Apples with Apples
Some interesting comments let me try and bring some light on a few things.
Zadara provides NFS / CIFS and iSCSI with HA built in, you don't need to stand up an additional EC2 instance to run the NAS or 2 to create HA, we provide access to the physical disks, dedicate CPU, Cache and networking so predictable performance.
We present the storage on a low latency direct connect to AWS typically 1-2ms latency.
This is a true multi-tenant solution, each customer has their VPSA mapped to their AWS account using a VPG in a separate network. We have multiple 10GB interfaces into each AWS facility so redundancy is built in. Our architecture is a scale out so a true multi-tenant cloud scale.
You can use CHAP and IPSEC to secure the data in flight, you can encrypt each volume, the key is not stored on disk by Zadara, neither we, AWS or anyone else but the customer holds this key.
The 3rd Party data centres that you talk about are hosting many of the worlds cloud infrastructures and are ISO 27001 accredited. If you do your research you may be surprised at who is hosting who within these 3rd party DC's.
Interesting the Comment that Zadara does not offer a Cloud NAS like SoftNAS.
To create a HA NAS with SoftNAS do you not need to create multiple EBS volumes and RAID them, then mirror this? So the Cloud NAS in this terminology is the fact that the NAS element is running on EC2 instances on EBS volumes. suppose it depends on how you define Cloud then. I always understood this as a turn up turn down pay for what you use and you don't care what it is running on as long as it meets your SLA after all you cannot dictate your hardware to AWS etc. can you?
Also you need to pick your EC2 instances correctly as you have northbound and southbound traffic through the SoftNAS heads, so you need to ensure you have enough network speed within these two instances to handle the data throughput and the mirroring. I suppose at the end of the day it depends on what you want to achieve and what levels of performance you need, if you want small scale, HA and performance does not matter too much then maybe the cost of SoftNAS on EBS is a better fit for you. If you want Enterprise storage in the cloud on AWS then its probably better to let Zadara customer s do the talking have a look at this case study
http://www.marketwatch.com/story/with-800000000-image-files-to-store-at-amazon-web-services-realty-data-uses-zadara-storage-and-rightbrain-networks-to-get-emc-caliber-performance-for-less-2014-06-24
I think the important thing is to decide what you want to achieve and at what cost, running XLarge instances to get a decent I/O performance may hurt the pocket a little after adding SoftNAS, PIOPS and 2 x EBS Storage. why not use the free trial option at Zadara to compare then decide.