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Moreover, there’s a dirty little secret in the storage industry. If you ask any vendor how many IOPS can be delivered by their devices in real world situations, there’s a good chance that you’ll get the same answer. Although many vendors will publish IOPS numbers – which I believe is a good practice, as long as the playing field is equal – those numbers are just a snapshot of a single array at a single point in time with a single kind of workload. In the real world, who knows what will hit that array? It’s impossible to test for every possible use case.
Let’s use cross-site mirroring via software RAID. Veritas used the concept of a plex which was just a mirror unit, or unit of protection. In this scenario, we present a same block-size LUN from each site, build a plex on top of each, and then create a volume on top. From this we provision a file system.
When partnered with Veritas Cluster Server (VCS), it made for simple scalable clusters that could be stretched over distance. Back in the early 2000’s, it was possible to deploy up to a 32–node VCS cluster. This was mainly due to the proprietary cluster communication protocols that imposed a lower overhead.