There are a couple of key differences between E-Series and FAS. The two product lines address significantly different needs
You are correct about E-series - it is block only - FCP/iSCSI. Without getting into the weeds about RAID/snapshot capability, etc., the core of E-series is speed. Lots of disks going as fast as they can with extremely low latency controllers and data paths. You can mix and match disk types from SATA to SSD and build up a large pool given the shelf types. At the end the core of E-series is fast block level storage.
FAS is a different animal. First, FAS is multiprotocol in one box. That is it can do NAS (CIFS/NFS) and Block (iSCSI/FCP/FCoE). But that is just the start. FAS is built around data management. To that end, FAS clusters can grow really big as you need them to. They support fully non-disruptive updates and replacement mechanisms with transparent data movement between elements of the cluster. FAS is software defined storage in that the physical space can be carved into many logical storage systems, each with separate domains of administration, access, and protocol. In short FAS is fully multi-tenant if you need that.
In addition, FAS has a rich set of data capabilities around efficiency, replication and protection, business continuity and disaster recovery, data preservation and compliance for those who need that built in as a standard part of the storage platform by design.
If your core need is fast block storage or gobs of block storage for which you don't need many bells and whistles, than E-Series presents as a screaming data delivery device or as a high capacity data storage device. Providing raw data for a Hadoop cluster for instance is a good use of E-series as one example where speed comes into play. Another is as the bulk storage behind an object store engine. In both cases external systems are providing the management intelligence. The E-series is the fast or big chunk of storage.
I've worked in a number of environments where FAS is used for both block and file as well. In these settings with the wide variety of applications it's easier to use the FAS storage features around data protection and replication as a central focus to backup/DR plans rather than try to implement something separate for each application. As a file sharing device it's very good at massive file counts - my last "customer" position housed about 8.5 Billion files in 3PB on FAS storage with another PB for block access. FAS is the jack of all trades giving you flexibility and control at the storage layer beyond most anyone's single platform.
Hope this helps you.
Bob Greenwald
Senior Systems Engineer | cStor
NCIE SAN ONTAP, Data Protection
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