Servers need RAM-based SSDs, not flash-based SSDs

How to store data? How to store data on servers? In the "good old days" (prior to 2012), servers used spinning platters of metal (disk drives) to store data. The introduction of SSDs complicated the issue.

SSDs (solid state disks) eliminate the spinning metal platters and use semiconductors to store data. Today one can purchase an SSD that plugs into a PC or server and acts just like a hard disk.

SSDs provide faster read and write times, lower power consumption, and greater reliability (mostly -- more on that later). Their cost has been higher than hard disks, but that has changed. Prices for SSDs are now in the same range as "classic" hard drives.

But life with SSDs is not perfect. The solid-state disks use flash RAM, which allows data to be stored after the power is off (something we want in our storage), but flash-based RAM is not that durable. The heavy workload that servers put on their storage systems causes failures in SSDs.

I'm sure that many folks are working on methods to improve the reliability of flash-based RAM. But for servers, I think there may be another path: classic (that is, non-flash) RAM.

We've been building RAM for decades. We know how to make it, in large quantities, and reliably. Classic RAM is typically faster than flash-based RAM, and typically cheaper. So why not use it?

The big difference in classic RAM and flash-based RAM is that classic RAM, when you remove power, forgets everything. An SSD built with classic RAM would work beautifully -- until you powered the unit off. (And even then you would notice the problem only when you powered it back on.)

The impression is that such an arrangement would be useless. I'm not so sure, for two reasons.

First, while desktop PCs are powered on and off regularly, servers are not. Servers are typically installed in data centers and kept on, twenty-four hours a day, every day of the year. If the server stays on, the data stays in RAM, and everything works.

Second, it is possible to build classic RAM SSDs with small, auxiliary power supplies. These small power supplies (usually batteries) can keep the RAM active, and therefore keep the data, while main power is not available.

RAM storage units are not new. They date back to the mid-1970s, and have been used on IBM mainframes, minicomputers, and even Apple II computers.

I suspect that at some point, someone will figure out that classic RAM makes sense for servers, and build SSDs for servers. This will be another step in the divergence of desktop PCs and server computers.