Yesterday’s post on IOPS vs latency provoked some controversy on Twitter. Kappy, CTO of a midwestern IT consultancy, asserted

@storagemojo Most AFA users don’t even care about latency. Sure there are latency sensitive apps, but data services are more important.

When asked what services, Kappy said

@lleung @storagemojo standard issue stuff. Snaps, replication, deep VMware integration, rich API access, etc. See:

I replied:

@Kappy Data services more important than performance? Really? What about the massive savings from lower latency?

Kappy replied:

@StorageMojo can you give more specifics as to what you see as “massive savings”?

The storage pyramid
Surprising question. As said in the StorageMojo post, not the tweet:

Lower latency means fewer inflight I/Os, less server I/O overhead and more server capacity. The systems can handle more work. With fewer servers, software licenses, network ports. Less power, cooling, floor space, maintenance.

Those massive savings. If flash isn’t making something better, you have to ask: Why has flash remade the storage industry in the last 10 years?

The StorageMojo take
Availability and performance are two sides of the same coin: low performance = low availability. That’s why tape’s high latency is slowly pushing it out of a market it once owned.

Most of the data services Kappy mentioned are designed to ensure availability because that’s what customers need. But the problem most data services help manage is simple: data corruption and loss.

There’s a reason we have a storage pyramid: if the cheapest storage were also the fastest that’s all we’d use. Flash has inserted itself between DRAM and disk arrays because it makes our systems perform better for a reasonable cost.

Data services are a Good Thing. But ask a customer if she’d rather have availability and performance or data services and you’ll find out quickly enough what customers care about.

Twitter isn’t the best place for a thorough airing of technical issues. But it can be educational nonetheless.

Courteous comments welcome, of course.