After extensive research on software-defined storage options and thorough tests, we selected StorPool for its product quality and high resource utilization.

I was not actively involved in the evaluation part. 

Over the years we have deployed numerous soſtware solutions including Nexenta, FreeNAS and OpenFiler, but in all cases we rapidly encountered scalability issues, performance problems or both.

Yes, compared to the storage system we used previously, StorPool is almost twice as fast.

We have tested several storage network solutions that our service providers had at the time: a Dell distributed storage used by SoftLayer (not sure on the exact platform/name but it was discontinued after if tailed spectacularly several times) and EMC (before it was acquired by Dell).

Before choosing this product, we also evaluated Ceph and GlusterFS.

We first tested open source solutions, Ceph and GlusterFS. GlusterFS is a good solution for file-based storage but it is slow for sync writing disk images. Ceph is also a good block storage solution but our test showed that on similar hardware StorPool outperformed Ceph by a large margin.

We are testing many software from open source to commercial solution for our distribution storage to host all our VPS like: Ceph Block Device, ZFS, Virtuozzo Storage, OnApp Integrated Storage, vSAN (VMware).

Yes, but we had bad experience with other vendors.