![]() ![]() ![]() When picking the right SSDs to set up an SSD cache for your NAS, you should evaluate SSD endurance by looking closely at two specifications: TBW (Terabytes Written) & DWPD (Drive Writes Per Day). Finding an adequate SSD that fits your IO demands is paramount since you don’t want your cache drive to wear out too quickly. The more frequently an SSD writes data, the shorter its lifespan will be. But there’s still a risk of data loss if the number of worn-out SSDs exceeds the fault tolerance in a RAID configuration. ![]() To ensure data safety, you need at least two SSDs to set up RAID 1 to allow fault tolerance of one SSD. Read-write cache: Compared to the read-only cache, the read-write cache writes data synchronously to the SSD.Because it’s not involved in writing data, data will remain safe and sound even when the SSD breaks down. Read-only cache: When you set an SSD as the read-only cache, only frequently accessed data is stored in the cache to accelerate random read speeds.The SSD cache can be categorized into the following two modes: Note that since large sequential read/write operations such as HD video streaming lack re-reading patterns, such workload patterns cannot benefit much from SSD caching. You can mount an SSD cache to a single storage volume or block-level iSCSI LUN to create a read/write buffer, enhancing random access performance. But fear not, there’s a way out - SSD cache. When running applications requiring higher random IOPS or when large amounts of data are written to non-contiguous blocks (e.g., OLTP databases and email services), building an all-SSD system can burn a hole in your pocket. Reserving a certain portion as the cache where hot data is stored, lower-latency SSDs can respond to data requests more readily, accelerating read/write speeds and boosting the overall performance. Now that we understand the difference, then what exactly is an SSD cache? It is the temporary storage space of frequently accessed data (aka hot data) on flash memory chips in an SSD. An SDD, however, has no moving parts and uses flash memory to store data, which consumes less power, causes nearly no noise, vibration and heat, and operates at higher speeds compared to a traditional hard drive. ![]() When dealing with high traffic of read/write requests (especially for a large number of small-sized files), the platter spins and read/write head keeps moving to search for data scattered on the drive in a non-contiguous manner. An HDD is composed of an actuator, read/write arm, spindle, and platters onto which data is stored. There’s an ongoing battle between HDDs and SDDs, both of which have their own pros and cons. ![]()
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