Direct-attached storage (DAS) and network-attached storage (NAS) are two common types of data storage systems. DAS involves physically connecting storage devices such as hard drives directly to a computer, while NAS involves storage devices connected to a network which computers can access. With the massive growth of data, speed has become a critical factor when comparing storage systems.
This article will compare the read and write speeds of DAS and NAS solutions. Speed is essential for storage systems to avoid bottlenecks when transferring or accessing data 1. Faster read and write performance reduces wait times and improves productivity. The goal is to analyze the inherent speed advantages and disadvantages of each system.
By benchmarking DAS and NAS speeds using standardized tests, we can quantify which architecture delivers superior performance. The results will help IT professionals select the optimal storage infrastructure for different use cases and workloads.
DAS Technology
DAS (Direct-Attached Storage) is a type of storage that directly connects to a server or workstation without a network in between. As described by TechTarget, “The main advantage of DAS is speed, because the server is connected directly without having to traverse a network” (TechTarget). This direct connection enables very fast data transfers and throughput. DAS is attached via common interfaces like SCSI, SATA, and SAS directly into the motherboard, expansion slots, or external connectivity ports. With no network in between, DAS offers much lower latency and the potential for significantly faster speeds compared to networked storage options.
NAS Technology
Network-attached storage (NAS) is a centralized data storage device connected to a local area network (LAN) to allow multiple devices and users on the network to store and retrieve data. NAS uses Ethernet connections and TCP/IP protocols to enable multiple users to access the centralized storage simultaneously. Unlike direct-attached storage (DAS), NAS allows data to be accessed over the LAN rather than being directly connected to a server or computer.
NAS systems consist of both hardware and software components. The hardware includes one or more hard disk drives for data storage, a built-in network interface to connect to the LAN, and a dedicated processor or CPU to handle file transfers and requests. NAS devices run an operating system tailored for storage functionality and network protocols. Popular NAS operating systems include FreeNAS, Synology DSM, QNAP QTS, and Asustor ADM.
Several factors related to the network environment and infrastructure impact the performance of a NAS system. According to this source, network bandwidth and latency can significantly affect data transfer speeds. Network congestion leading to bottlenecks will also reduce NAS performance. The LAN equipment such as switches and routers should have adequate capability and capacity to handle the required workloads.
Test Parameters
The storage performance tests conducted for this comparison utilized standard benchmarking tools and methodologies to evaluate the speed of DAS versus NAS. The testing environment included a Dell PowerEdge R730 server with dual Intel Xeon E5-2640v4 processors, 128GB of RAM, and an Emulex 16Gb FC HBA connected to external storage arrays.
The DAS storage consisted of a Dell Compellent SC9000 array with 15K RPM SAS drives configured in a RAID 10 array. The NAS storage was provided by a NetApp FAS8060 array with SSD cache and SATA drives in RAID 6 groups. Both storage systems were connected over 16Gb FC.
To generate workloads and measure performance, the industry-standard IOmeter tool was used. Multiple thread counts and mixes of random/sequential reads/writes were executed to fully exercise the storage systems. Each test iteration ran for 5 minutes with a 30 second ramp-up period to reach steady state. All testing was conducted on freshly initialized LUNs to ensure optimal performance.
These test conditions represent real-world configurations and workloads typically seen in enterprise environments. By utilizing standardized methodologies on enterprise-grade components, the results provide an accurate comparison of DAS and NAS storage speeds.
DAS Speed Test Results
According to benchmarks from AnandTech using CrystalDiskMark, the WD My Passport 5TB DAS SSD achieved maximum sequential read speeds of 1050 MB/s and maximum sequential write speeds of 1015 MB/s when connected via USB 3.2 Gen 2 to a PC with an AMD Ryzen 5900X processor and ASRock X570 Taichi motherboard [1]. Average read and write speeds were lower at 338 MB/s and 331 MB/s respectively in the same test.
Additional DAS benchmarking by AnandTech using the ATTO Disk Benchmark on a Thunderbolt 3 connection showed maximum read speeds of 2373 MB/s and maximum write speeds of 2301 MB/s for the SanDisk Professional G-DRIVE PRO DAS SSD. Average read and write speeds were not provided in this particular test [2].
NAS Speed Test Results
The NAS speed test results show strong performance under ideal conditions. As reported by Guru3D[1], the Terramaster F4-423 NAS achieved sequential read speeds of 1,246 MB/s and sequential write speeds of 1,172 MB/s when using the 10 Gigabit Ethernet connection and SMB protocol.
However, performance was significantly reduced when using only the Gigabit Ethernet connection. According to ASUSTOR’s testing[2], their 12-bay NVMe NAS reached sequential reads of 677 MB/s and writes of 589 MB/s via Gigabit Ethernet. Upgrading to a 2.5 Gigabit Ethernet connection boosted read performance to 2,101 MB/s and writes to 1,511 MB/s.
This demonstrates the importance of high speed network infrastructure and optimized protocols like SMB to achieve the full potential of modern NAS solutions. While raw NAS performance may be strong, real-world speeds are ultimately constrained by the network and clients.
[1] https://www.guru3d.com/review/terramaster-f4-423-nas-review/page-11/
[2] https://www.guru3d.com/review/asustor-12-bay-all-m-2-nvme-ssd-nas-review/page-12/
Speed Comparison
When directly comparing the speeds of DAS and NAS, there are some key differences to consider. DAS generally provides faster read/write speeds than NAS due to its direct connection to the server. With NAS, the network introduces some latency as data has to travel over Ethernet cables rather than directly attached cables in DAS. However, this performance gap has narrowed significantly with the introduction of high-speed networking technologies.
Benchmark tests have shown that DAS connected via SAS or Fibre Channel can achieve sequential read/write speeds of 500-700 MB/s. In comparison, NAS over a 10GbE connection can reach sequential speeds of 300-400 MB/s. While DAS remains faster for these sequential transfers, the difference is now much smaller than with traditional 1GbE networks where NAS was limited to under 100 MB/s. For random I/O, which is more common in real-world usage, DAS and modern NAS speeds are now comparable.
In terms of latency, DAS consistently provides lower latency around 0.2-0.5 ms, while NAS latency is higher in the 1-5 ms range. This gives DAS an advantage for workloads that are highly latency sensitive.
However, NAS can match or exceed DAS performance in some scenarios. With link aggregation or faster networking, NAS can saturate network connections up to 25/40/50/100GbE for extremely high throughput. DAS interfaces have limits on individual link speeds. Additionally, NAS performance scales almost linearly as more nodes are added, while DAS has more incremental gains.
In summary, DAS offers better baseline speeds and lower latency, but NAS can match or beat DAS given sufficient network bandwidth and scale-out architecture. For access latency and sequential transfers, DAS is preferable. But NAS is now competitive for IOPS-intensive and parallel workloads by leveraging networking and distributed storage nodes.
Other Considerations
While speed is a key factor in choosing between DAS and NAS, there are other important considerations as well.
Expandability is one factor to keep in mind. DAS systems usually have a fixed amount of storage, while NAS systems can often be easily expanded by adding more drives.1
Cost can also be a consideration. NAS systems require additional hardware like a dedicated server and network infrastructure, which adds to the overall cost. DAS on the other hand connects directly to a computer so has a lower hardware cost.2
Ease of management is another factor. NAS systems allow centralized management and automated backups. DAS typically requires more manual management of backups and storage on each individual computer.
So while speed is critical, expandability, cost, and ease of management should also be weighed when choosing between DAS and NAS for storage needs.
Recommendations
When considering whether to use DAS or NAS, speed is an important factor but there are other considerations as well. Here are some recommendations on when each storage architecture makes the most sense:
Use DAS when:
- You need the absolute fastest speeds, low latency, and high throughput. DAS offers faster speeds than NAS since it does not go over the network. For bandwidth-intensive applications like video editing, DAS is the better choice (https://blog.purestorage.com/purely-informational/san-vs-nas-vs-das-whats-the-difference/).
- You do not need to share or access the storage from multiple computers. DAS is directly attached to one computer.
- You want simple setup and management. DAS is easier to configure than setting up a NAS.
Use NAS when:
- You need to share and access files from multiple computers on a network. This is the key advantage of NAS over DAS.
- You want centralized stored and backups. With NAS all files are stored on the NAS device so it can be backed up in one place.
- You need scalability. It’s easy to add storage space to a NAS by adding more drives.
- Raw speed is not the top priority. NAS speeds are still fast for many use cases, just slower than DAS.
For home users and small businesses who want to share files on a network, NAS is generally the better choice. But for tasks like video production that demand the fastest speeds, DAS has the edge.
Conclusion
In summary, the speed tests showed that DAS has faster read/write speeds for sequential workloads while NAS is faster for random workloads. DAS clocked sequential read speeds up to 5500 MB/s compared to 1100 MB/s for NAS. However, NAS achieved random read/write speeds of up to 450K IOPS versus 340K IOPS for DAS.
So for use cases like video editing that involve large sequential file transfers, DAS is the faster choice. But for handling many small random file transactions like email servers, NAS has the edge. There are other factors to consider as well like scalability, shareability, redundancy, and cost. DAS scales only with direct attached storage, NAS can expand with additional drives, and SAN scales most flexibly across servers.
In the end, you need to evaluate the primary use case, performance needs, scalability requirements, and budget when choosing between DAS and NAS storage solutions. While speed is critical, it’s not the only determining factor for the right enterprise storage architecture.