Integrating The SSD Appliance

The SSD Appliance or Memory Array applies to storage systems that are designed from the ground up to only be used with solid state storage. They are often focused on storage I/O performance and solid state integrity more so than providing storage services like snapshots or replication. In this entry we will look at when does it make sense to use these products instead of adding SSD to an existing storage system or going all out and buying a new solid state storage system.It sometimes goes unnoticed but the solid state appliance has been available for much longer than the current hype cycle would lead you to believe. I worked on my first SSD project almost 20 years ago, speeding up the database transactions at a major oil and gas company. The good news is the process of integrating these systems has improved greatly since then. That system was a RAM based device with a whooping 4GB of RAM and cost almost $350,000. Not only did we have to be careful about integration but also had to deal with the realities that the storage was volatile, a loss in power meant total data loss.

The design was to hold transaction logs for the database application responsible for oil and gas futures trading. Speed equaled money. Because it was RAM based the system had its own built in battery backup, a backup hard drive, it was on a UPS and copies of the data in the device were made to hard disk drives internal to the server (this was before SANs) every hour. In other words the integration was a very manual process and great lengths were taken to protect the data on that device.

Fast forward twenty years and we see that flash memory has made things easier as has advancements in software. Since flash is persistent and there is not the risk of loss like there was with a RAM based device, much of the integration pressure is alleviated. The price of solid state storage has come down significantly since then as well. We practically give away 4GB of memory on thumb drives now.

The manual process of integration is still commonplace today and really there is nothing wrong with it. If you have a very discrete set of data that can benefit from the performance improvement of solid state disk, moving the hot files or now the entire data set to solid state storage is very viable. You have to make sure that the data is protected either as we did above or by specifically backing up the solid state storage area. While the management of this device is separate from your normal storage process, in my experience because of the high profile value of solid state storage qualifying data, most organizations can handle the extra management without too much difficulty.

The overwhelming advantage of this more "raw" form of integration is there are no introductions of layers of latency that software management may bring. The software solutions clearly have their role to play and can ease the overall integration process. While they will introduce some level of latency, the solid state solution, in almost every case I've seen, remains significantly faster than mechanical drives. As long as that latency does not impact your overall performance then you can add these services and make your integration process and ongoing management easier.

There are several ways to add data services to a solid state storage appliance and integrate it into an existing storage platform. First there is the storage virtualization software that can integrate a variety of storage types into a single set of storage management services. Then from a management perspective you are dealing with a single tool set to trigger snapshots, replication and other data services. In addition to the storage only solution there is also the capability to leverage an operating system or hypervisor to provide these services. This can be in the form of a preferred mirror as we discuss in our article "Integrating SSD and Maintaining Disaster Recovery" or it can be a more thorough feature set like snapshots and replication. Most hypervisors for example have a surprisingly robust set of capabilities that can integrate solid state disk with storage.

Another alternative is for the storage virtualization application, OS or hypervisor, just to use the storage area as a very large cache. This will mostly help you only on reads although there are some solutions that will allow the solid state appliance to act as a cache for both reads and writes. The caching concept is one that should have great appeal to many environments looking for widespread use of solid state storage instead of just an isolated case.

The point is don't let the fact that the solid state appliance is focused on storage performance specific capabilities more so than storage services stop you. Especially if you have a relatively finite data set that can benefit from solid state that can be the ideal solution and have minimal impact on overall storage management time.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.