All-Flash vs. Hybrid Storage

Within the past few years, there has been a steady increase in the number of companies investing in flash-based storage arrays. With the price of SSDs going down year after year, SMBs and SMEs are now able to justify purchasing a flash-based unit due in a large part to their sheer performance benefits. Who can blame us for wanting these high performing units that provide high IOPS counts and low latencies to our infrastructures? This seems like a no-brainer, right? When choosing a flash-based unit, we are handed two options….Hybrid storage or All-Flash storage. Before we discuss the benefits of each type of array, let’s first talk a bit about the differences between Hybrid storage and All-Flash storage.


Hybrid SANs

StorTrends Hybrid StorageA Hybrid SAN consists of both SSDs and HDDs. In a hybrid unit, the SSDs are used for hosting the hot or most frequently accessed data, and are used as either a cache or as a tier. By doing this, you will see substantial acceleration of reads and writes both to and from the storage array. Some vendors, like StorTrends, have both caching and tiering in their hybrid SANs to truly get the most out of this acceleration.  Other vendors may have solely caching or solely tiering. Regardless, these SSDs will speed things up in your infrastructure, and Hybrid arrays are going to have around 5 milliseconds of latency depending on the workload. Compare this to the 20 milliseconds + of latency you would typically see with a traditional spinning disk unit, and you’ve got yourself vast improvement!

Enough about these high performing SSDs. When discussing hybrid storage, you can’t forget about those pesky spinning disks. While the SSDs are used for hosting the hot data, these lower performing HDDs are used for hosting the cold or least frequently accessed data. By utilizing the more expensive SSDs for hot data and the low-cost HDDs for cold data, you are able to get the most out of your storage unit while doing so at a very reasonable price point.


All-Flash SANs

StorTrends Hybrid StorageWhile a Hybrid SAN consists of both SSDs and HDDs, an All-Flash SAN consists of only SSDs, and there are no moving parts in the system. The SSDs host both hot and cold data, and are used for both caching and tiering.  All-Flash arrays are going to see latency between 1 and 2 milliseconds, and sometimes will even fall below 1 millisecond of latency depending on the workload. This is pretty crazy when compared to the spinning disk units we all seemed to have been using just a few years back, isn’t it? While All-Flash units are typically going to be more expensive than a hybrid array, they offer lower operating expenditures (OPEX) through decreased power consumption, rack space, and management hours.

Hybrid or All-Flash? Which Should you Choose?

It’s easy to see that hybrid units provide great value by utilizing the expensive, high performing SSDs and low-cost HDDs together in a single unit. These units are great for a number of environments. Particularly those environments that have an abundance of user data that does not require high performance, but does have a handful of data creating a heavy I/O load.


All-Flash SANs are great for environments in need of a high performing solution. For example, virtual environments and environments that utilize VDI are prime candidates for all-flash storage. Also, if you are looking for an extremely scalable solution, then All-Flash is for you. You are able to add databases, applications, and users on the fly. There is also less downtime, and you have no failing HDDs (mechanical to replace).

The bottom line here is that whether you should go with a Hybrid SAN or an All-Flash SAN depends entirely on your environment, and there are a number of factors that affect this decision. There are benefits to both arrays, and it is essential that you know everything about your environment prior to purchasing a storage solution.  Capacity utilization, IOPS usage, reads versus writes, network bandwidth performance, server statistics, hot data versus cold data, and application performance all play into which type of storage unit you should choose.


StorTrends offers a free data analysis tool called iDATA that provides a detailed report of your IT infrastructure, and gives you the metrics. You can download the tool for free to see which type of array makes sense for you!