The Celerra is EMC's entry into the ever competitive NAS (Network Attached Storage) market. With this, they go head-to-head with the industry leader, Network Appliance (NetApp).

The Celerra architecture lends itself much better to scaling up for very, very high performance. They separate the NAS logic from the disks in completely separate cabinets. (Unlike NetApp which requires that you buy NetApp-specific disks to put in the same cabinet.) In the NFS benchmarking wars neither vendor seems to run the same benchmarks as the other, and both claim better performance. My personal read on things is that NetApp performs better in the benchmarks, but there are probably more important criteria to use for deciding which to buy.

Both systems require specialized knowledge and training in order to use them properly. The Celerra is less maintenance overall since more can be offloaded to EMC. This is great if you can cope with the 5-day delays before any change can go in. (In some of the ummm... more "dynamic" environments I've worked in, this 5-day delay was a blessing since it gave everyone time to reflect on the wisdom of the change before it went in.) In some environments this EMC-centric change methodology will be a big problem, hence the dual pro/con for EMC installation.

Neither system is particularly easy to learn to operate, and they both use completely different command sets to manage. NetApps, as the industry leader, have a wider base of people familiar with them. Hiring administrators who already know NetApp will be significantly easier than hiring those who already know Celerra.

The best part about a Celerra is the separation from the storage (disks) themselves. You don't need to go and purchase expensive dedicated disks for the NAS storage. At the time I was using the Celerra it did not yet integrate into a SAN solution, but that support was forthcoming. I suspect they have it now. This allows support for the EMC "storage consolidation" model which saves on wasted disks sitting unallocated inside multiple independent hosts.

I had problems getting the Celerra to fail over properly in the event of an external NIC or switch failure. At the time we determined that the Celerra did not support the ability to fail over if they upstream (client side) NIC failed or its switch failed. We finally resorted to a nasty unsupported EtherChannel trunking configuration whereby a single NIC or single switch could fail and the EtherChannel would handle the failover. I suspect EMC has corrected this oversight by now, but best to verify!

The NFS protocol is highly nonstandard. Each vendor applies their own interpretation of the standard and their own performance tweaks. NFS is probably one of the least interoperable of all the common network protocols. Because of this, subtle bugs appear all the time. Subtle bugs in any sort of data storage system are particularly nasty since filesystem writes are permanent. (Even transient errors can therefore become permanent problems.) For this reason, the stability of the NFS software/firmware is very, very important. As the new guy, the Celerra has the disadvantage here. NetApps have the advantage of many many years of dealing with stupid NFS bugs.

The Celerra is best suited for people with an existing EMC disk investment they want to make the most of. For a company just starting out or one without an existing EMC investment, the more widely supported and widely installed NetApp is probably a better choice.

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