In a world where roles like Data Analyst, Data Engineer, Database Administrator, Data Scientist, and Data Architect are in high demand, it is evident that, data collection, preservation, and analysis of are of paramount importance. We are endlessly dependent on data, particularly in businesses. As such, companies are particularly vulnerable to hacking, natural disasters, and other forms of data loss these days. Distributed caching is another avenue heavily dependent on data. With these vulnerabilities prompting such uncertainty, several distributed caching platforms (like NCache & Redis) offer their customers a Persistence store. Persistence means data is written to a specific location for durable storage and reliable backup, providing their customers with much-needed peace of mind.
Why is Persistence Necessary?
But why is such a backup necessary for distributed caching when we tend to expect volatility in such a platform? And, why is it so important, when cache data is typically derived from other sources???
If you lose all your cache data—whether by accident, catastrophic failure, or node maintenance—your application will need to slowly reprocess all the pre-existing data. This repopulation process can become a major headache, if accessing the original data source is expensive, either in time or money. This is where having a persistence store in your caching solution can be incredibly beneficial. But which solution offers the best option? Let’s dive in and find out.
Redis Vs. NCache Persistence Store
First, we need to understand what these two persistence stores entail, before we can decide which is better.
How They Work
NCache’s entire technique for updating objects in the persistence store is asynchronous and employs a persistent queue which spares you any unnecessary waiting time. A background thread simply examines all operations in this queue (at predefined intervals) and copies them to the store as is – while you continue with your work. So, when you perform write operations, the cache loads the data into memory before adding it to the store.
Figure 1: The detailed process of data persistence and loading in NCache.
On the other hand, Redis offers three options for persistence; RDB (Redis Database), AOF (Append Only File), and a combination of RDB + AOF. RDB employs snapshotting, i.e., making copies of your dataset at periodic intervals.
AOF is more like an operation log. It merely catalogs any and all write operations as they take place. When used together, AOF and RDB present a complete picture of the processes taking place within a cache.
Why is NCache better than Redis?
The following are the reasons why NCache’s persistence store is better than Redis.
Increased Backup-interval & Reduced Chances of Data Loss
First and foremost, NCache allows users to set an interval of their choice from a second onwards – which minimizes the chance of cache data loss. Alternatively, Redis only offers a few options for backup times, (i.e., no backups, every 1 hour, every 6 hours, or every 12 hours), which might not be sufficient for minimizing data loss). Even Redis acknowledges that their RDB is not ideal for preventing data loss, particularly, when dealing with Power outages, etc.
No Unnecessary Memory Consumption
NCache only creates one version of the persisted data that is constantly updated using optimized queues. This process is much more memory-efficient compared to Redis. For instance, the snapshotting process creates multiple copies of your database, which consumes memory unnecessarily. AOF files are usually even larger than their equivalent RDB files, even when considering the same dataset. While Redis claims the ability to rewrite the AOF in the background when it gets too big, even this process involves creating a brand-new file. And this rewriting would be completely unnecessary if you opt to use NCache.
Asynchronous Backup Operations
NCache handles persistence asynchronously through a dedicated queue, ensuring that enqueued data remains intact even if it cannot be immediately written to the persistence store. On the other hand, Redis employs the fsync policy to record operations for its AOF option. By default, this mechanism uses a background thread for write operations. Unfortunately, the thread can only perform these operations when no fsync is in progress, which may delay data persistence and increase the risk of data loss.
Near Real-Time Operations & High-Availability
As we’ve discussed NCache offers users with the ability to set very short time intervals. Therefore, despite being asynchronous, the data persistence is almost real-time, without compromising application performance. Meaning how there is little to no chance of data loss with NCache persistence, especially compared to Redis.
Moreover, NCache ensures that even if data has not yet been loaded back into the cache cluster, the application can still access it. If this process is yet to be completed in memory, NCache automatically reads it from the persistent storage.
Disaster Recovery
Speaking of data loss, when things go catastrophically wrong, with NCache you have access to all your data upon cache restart. Whereas with the alternative, you only have several outdated versions of the data due to the large persistence intervals.
Optimized Queues
Moreover, if two write operations occur, one to update an operation and other to delete it, NCache’s optimized queue will simply delete it instead of performing the unnecessary update. Unfortunately, the Redis’s logging process does not account for such redundancies and wastes resources logging it.
Other Features
Lastly, while it is observable that the persistence store is a more powerful feature in NCache it offers a variety of other very powerful features. For instance, if you are intrigued by the possibility of viewing your dataset as it was at a certain point in time, NCache offers users the option to Import/Export cache data. Similarly, it also offers extensive monitoring capability beyond the NCache Logs (which are a more optimized version of AOF), it offers monitoring tools via the NCache Management Center, Command Line Tools, various PerfMon tools, SNMP Counters, and third-party tools like Grafana and Prometheus.
Conclusion
Clearly, NCache offers users the best of both worlds when it comes to persistence. And that is without even mentioning the series of easy-to-manage and configuring tools you’ll get as a bonus even if your primary concern is persistence. So, what are you waiting for? Download NCache now and sign-up for your 30-day free trial!
