Is CLARiiON a 5×9s Box?

Is CLARiiON a 5×9s Box?

Often I find myself engaged in projects where I am asked to document current storage tiers and develop future state tiers of storage. In characterizing each tier, performance and availability are among the key metrics that define each tier. There is the perception with some IT professionals that CLARiiON is a 5×9s storage platform. It seems that the justification of availability classification depends on who you talk to.

If you look through EMC’s literature, they seem to reference perceived availability based on their customer’s uptime, not as a design spec. This leaves us a subjective sampling of configurations that EMC would undoubtedly pick only the most redundant and stable.

So I can take a couple of Iomega USB drives, and with the right software and configuration, I could also meet 5×9s over a 1yr time period. This doesn’t mean that one of those USB drives meets a 5×9s design spec. Ok, maybe I’m overreaching a bit, but you get my point.

Symmetrix traditionally has been a closed architecture that requires EMC SEs and SAs to configure, update, make bin file and firmware updates. In the past there were a lot more changes on a Symm that required downtime than today. That being said, they’ve always touted the Symm as being 5×9s. Is the criterion for 5×9s a sliding metric? So I’m not even sure scheduled downtime should be considered in 5×9s.

The CLARiiON on the other hand is more open to customer configuration, reconfiguration etc… This makes it subject to hardware downtime. I know, this is a sweeping statement but I have Murphy’s Law behind me. The fact that a Symm requires EMC engineers to schedule and make critical changes kind of reminds me of the seatbelt in my Subaru. It is !!SO!! annoying that you have no choice but to put it on to stop the “fasten your seatbelt” alarm. Seatbelts are the one thing that protects passengers most in an accident, and most affects the car’s safety rating.

So there are 3 ways I hear people referring to uptime or availability

• Perceived availability – Metric driven by field performance
• Downtime for maintenance – I disagree with this one. This sound more to me like serviceability rather than availability
• Unplanned downtime – Influenced (reduced) by redundancy in architecture. I think this is the real metric that should define availability – 4×9s vs. 5×9s

So, I’m inclined to say that the CX-3 with active passive controllers would not be 5×9s but the CX-4 would. I would only consider chassis redundancy in the CX or DMX availability metric, so just up to the controller. This would not include redundant FA or host paths. As long as there are two controllers with two active/active paths to the SAN, I’d consider it 5×9s. After that it’s up to the SAN to provide redundancy to the host. I would also not include RAID configuration in this metric.

By James Brissenden, GlassHouse Senior Consultant, Storage and Data Protection

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