SSD Cache feature is a storage performance improvement solution that stores the most frequently used files or “hot” information to low latency Solid State Drives (SSDs) to improve system performance continuously. Here we will see how SSD cache functions in NAS storage and whether it is worth using SSD caching.
Difference between SSD Cache and primary NAS storage cache
SSD Cache is a secondary cache used in conjunction with the primary cache or DRAM cache within the NAS storage controller.
SSD Cache operates differently than primary cache. In the primary cache, data is saved in DRAM after a read operation.
SSD Cache is only used when it is determined that it is beneficial to store the information in the SSD cache instead of the primary cache to enhance the system’s overall performance.
With SSD Cache, the data is copied from the volumes and is stored in two RAID internal volumes, which are automatically generated when you create the SSD Cache.
Internal RAID volumes serve as internal cache processing functions. They are, however, not visible or accessible through the interface.
How SSD Cache is utilized in NAS storage
Many manufacturers like Stonefly employ intelligent caching in their NAS storage appliances. Smart caching is available in the best NAS systems that puts frequently used data dynamically on the drive with lower latency so that responses to data requests are quicker. If a program needs data stored in the cache, the drive with lower latency will be used. If not, the data is taken from the slower drive. The more the information is stored in the cache, the more the performance increases.
When a host application accesses drives on the array, the data is saved in the SSD Cache. If the host program again requests that data, it reads out of the SSD Cache instead of the hard drives. The most frequently used data can be found in the SSD Cache. The drives are only used when the data can’t be read from the SSD Cache.
Is SSD cache in NAS storage worth it?
Spinning hard drives have limited write performance, so adding an SSD to a NAS device can provide a significant boost.
SSDs typically provide faster read speeds than spinning hard drives. But they can also write data 10 to 20 times faster than a spinning hard drive. The SSD cache is used to store data while it’s searched temporarily, and it uses SSD’s performance to speed up the process.
SSD cache in NAS devices works the same way as the system. The system checks the available cache memory first. Then, if it can read the data it needs, it retrieves it from the cache instead of accessing the primary storage. In case the cache isn’t large enough or the data isn’t available, the system checks the HDDs. This process can significantly improve the performance of your NAS storage.
Bottom Line
Caching data makes sense for Network Attached Storage devices with a small amount of data, but it can also degrade performance as the amount of cached data grows.
For some manufacturers, SSDs aren’t an option because the cost would be prohibitive. But spinning hard drives don’t offer the same performance as SSDs, so caching can help speed up NAS storage without having to install much expensive hardware for scaling out your storage appliances.
