With the cost of flash decreasing, many businesses have started looking into incorporating flash storage into their storage systems. Like every other technology, it’s very important to learn about the vendor and the features of their particular product so performance isn’t affected by a poor configuration. Here are some key factors to look into before selecting a flash storage vendor.
The exact terminology vendors use for the equipment available to expand your storage space tends to vary, but the important thing to find out is if the LUNs distribute across all the units of the expansion. If the LUNs don’t distribute, their capacity and performance will both be limited. In addition, a true scale-out system should increase performance linearly by adding additional units to the storage system. In other words, the number of IOPS you can extract should be from a single LUN, rather than the sum total of multiple LUNs.
If the vendor requires that the host and application configuration be changed every time you expand, the frequent disruptions will quickly add up in lost productivity and other costs. Instead, look for an option that doesn’t require you to change the configuration in order to scale.
There are two types of snapshots: redirect-on-write and copy-on-write. Copy-on-write snapshots tend to have a negative impact on performance because write requests will be delayed while the data is being copied to the snapshot pool. A good sign that you have copy-on write snapshots is if the vendor recommends scheduling snapshots during low-load times.
An additional aspect to consider about snapshots is how much management overhead it is going to require. The more you have to set up and manage the snapshots yourself, the more likely it is that you will lose many snapshot features. One particular feature to look out for is if the snapshots are chained. Chained snapshots are dependent on each other, so it’s impossible to delete an individual snapshot, and the recovery process is incredibly slow.
Certain vendors may not have the ability to add additional external capacity to the existing system, and instead require adding an entirely separate system that is connected to the original via software. This type of setup dramatically increases the complexity of your storage system, and complexity always runs the risk of affecting system availability and performance, as well as hidden costs.
It’s important for the system to be able to run multiple types of workloads simultaneously. Unfortunately, many arrays are only built for one particular type of workload, such as OLTP, so they will sacrifice bandwidth or performance in order to optimize the other factor. In this case, data will end up being siloed based on workload, leading to extra costs and management overhead.
Arrays with a fixed block size are optimized for only one type of workload, such as a small block size is optimized for an IOPS-intensive workload. On the other hand, variable block sizes permits an array to adjust to the best size for each application, optimizing its performance for any workload.
Be sure to dig into the details of what each vendor offers before purchasing a flash array storage solution. The aspects mentioned above are a good place to start, as they directly impact the cost of maintaining the system as well as its cost. What other factors have you found to be important when selecting a flash vendor?