Network-attached storage (NAS) and direct-attached storage (DAS) are two common storage solutions used by businesses and organizations. NAS devices connect to a local area network (LAN) and allow multiple users and devices to access files simultaneously. DAS devices connect directly to a computer or server. While NAS provides more flexibility for sharing data, DAS offers some unique advantages in performance, security, and cost that make it a better choice in certain situations.
Quick Summary of Key Advantages of DAS over NAS
Here is a quick overview of some of the main benefits of using DAS rather than NAS:
- Faster access speeds – DAS has higher throughput and lower latency.
- More reliability – DAS doesn’t depend on network availability.
- Better security – DAS is not exposed on a network.
- Lower cost – DAS hardware is less expensive than NAS.
- Easier scalability – Expanding DAS capacity is straightforward.
- Simple setup – DAS just needs to be plugged into a server.
DAS Provides Faster Access Speeds Than NAS
One of the biggest advantages of DAS over NAS is faster data access speeds. DAS connects directly to a server or computer using high-speed interfaces like SCSI, SAS, or SATA. This provides much higher bandwidth and throughput compared to NAS devices that rely on 1Gb or 10Gb network connections. DAS bypasses the network entirely, eliminating a major bottleneck that can limit NAS performance.
Benchmarks of DAS vs. NAS consistently show large differences in throughput. High-performance DAS can deliver over 1GB/s of sequential read/write bandwidth. High-end NAS devices top out at around 200-300MB/s for sequential transfers when accessing data over a 10Gb LAN connection. The direct connection of DAS removes the latency of going over the network, providing microseconds of response time versus milliseconds for NAS.
For use cases that demand low-latency and high bandwidth access to storage like high-performance computing, virtualization, big data analytics, and gaming, DAS is vastly superior to NAS in speed. Applications that do large sequential reads and writes or random IOPS will see big performance advantages with DAS.
Use Cases Where DAS Speed Advantages Shine
- High-performance computing clusters
- Data analytics platforms
- Database servers
- Virtualized environments
- Transactional applications like ERP, CRM, ecommerce
- Gaming servers
DAS Provides Higher Reliability Than NAS
In addition to faster performance, DAS also provides more reliable data access than NAS. Because it does not depend on network availability to connect servers to storage, DAS eliminates a big point of failure. Network connectivity issues, congestion, or outages will immediately render NAS storage unavailable. With DAS, connectivity failures are taken out of the equation. DAS remains accessible as long as the physical connection between the server and storage is intact.
Having your storage performance and accessibility rely solely on direct connections also simplifies troubleshooting when issues arise. With NAS, tracking down connectivity problems across complex LAN environments can be difficult. With DAS, either the server can see the storage or it can’t. There is no need to account forpossible problems like:
- Network interface card failures
- Flaky network cables and switch ports
- VLAN misconfigurations
- Spanning tree protocol loop issues
- Inadequate network teaming and lack of redundancy
- Overutilized network segments
- Incompatible networking hardware
While modern NAS solutions often have redundancy mechanisms to minimize disruption, these add cost and complexity. DAS provides inherent reliability that NAS cannot match. This makes DAS ideal for mission-critical systems that demand 24/7 availability.
Use Cases Where DAS Reliability Shines
- Real-time transactional databases
- High-volume ecommerce applications
- Trading systems and financial applications
- Industrial control and manufacturing systems
- Hospital and medical systems
- Public safety and emergency response systems
DAS Provides Stronger Security Than NAS
With NAS devices connected directly to a network, all of the data on them is accessible to anything else on that network. This exposes NAS to more potential security risks than direct-attached storage. While permissions and network segmentation can limit access, NAS is still fundamentally more vulnerable than keeping data isolated on DAS devices.
DAS keeps data off the network altogether, completely eliminating many vectors of attack. If DAS disks are only connected directly to a single, secured server, the surface area for threats is greatly minimized. The data cannot be accessed externally, keeping it safer from risks like:
- Malware or ransomware spreading on the network
- Breaches originating from other compromised endpoints
- Network sniffing or man-in-the-middle attacks
- Brute force or password spraying on NAS shares
- Exploiting vulnerabilities in NAS services and protocols
While locking down and hardening NAS security is possible, it often requires complex governance of permissions, ACLs, firewall rules, and so on. DAS sidesteps these issues by avoiding connections outside of the storage server entirely. The simpler approach of DAS makes strong security much easier to achieve.
Use Cases Where DAS Security Shines
- Stores of highly sensitive data like financials or medical records
- Meeting regulatory compliance requirements like HIPAA
- Safeguarding intellectual property and proprietary data
- Isolating top secret government and military data
- Hardening security on compromised networks
DAS Storage Has a Lower Cost Than NAS
The dedicated hardware required for NAS creates a cost premium over relying on DAS. A NAS appliance that provides the protocols, networks connections, and management software will generally cost more than an equivalent DAS disk shelf or JBOD enclosure.
For large amounts of storage capacity, a NAS system also requires investment in 10Gb (or faster) networks and switches to avoid creating a network bottleneck. High-performance networks add significant cost on top of the NAS hardware itself. DAS connectivity relies on relatively inexpensive SAS, SATA, or SCSI cables.
The simplicity and focused nature of DAS devices also translates to lower long-term costs. NAS appliances have much more that can go wrong with both hardware and software components needing attention. DAS just provides raw disk capacity without the overhead of an operating system, network stack, and added hardware to fail.
Administrative costs are also lower with DAS since there is no need to manage NAS related functionality like protocols, access control lists, network shares, etc. DAS requires minimal management once configured, saving IT time and salary expense.
Use Cases Where DAS Lower Cost Shines
- Cost-sensitive environments like SMBs and remote offices
- Maximizing storage capacity on a tight budget
- Getting high performance without expensive networking
- Complementing existing NAS with additional low-cost capacity
DAS Scaling is Simpler Than NAS
When growing storage capacity requirements, DAS solutions offer easier and more modular scaling than NAS. Adding capacity to DAS is as simple as connecting new disk enclosures to available ports on the server. DAS connectivity protocols like SAS allow chaining together multiple shelves.
NAS scaling requires ensuring the network infrastructure can handle increased storage and load. Expanding NAS often means expensive upgrades to 10/25/40/100 GbE networks and switches to handle extra throughput. Bottlenecking the network defeats the purpose of adding more NAS capacity. With DAS, there is no network bottleneck to consider.
The operating systems and supporting hardware on NAS appliances also impose limits on scalability. Vendors often sell different NAS models to accommodate different capacity ranges. Exceeding those ranges requires potentially disruptive migrations between NAS hardware generations or platforms. DAS has no such artificial limits, just connections for more disk.
Use Cases Where DAS Scaling Shines
- Adding storage to existing servers, incrementally as needed
- Supporting growth without big upfront investments
- Avoiding the cost of overprovisioning NAS for future growth
- Building out hyperscale server farms and data centers
DAS is Simpler to Set Up Than NAS
For quickly adding storage to a server, DAS solutions require far less effort to get up and running than NAS. The initial hardware installation is just connecting DAS disk enclosures via cables to ports on the server. There is no networking configuration needed. The DAS disks appear as local storage on the server. All the complexity of protocols, network shares, access control lists, etc. is avoided.
Adding NAS requires configuring IP addresses, network ports, VLANs, and ensuring routing is set up correctly across network tiers. Additional steps are necessary to define NAS shares, allocate capacity, and permit access to specific servers or users.
The learning curve is also steeper for NAS, requiring deeper networking, administration, and storage management skills. DAS just presents like ordinary internal or external disks, requiring no specialized NAS knowledge.
Use Cases Where DAS Setup Simplicity Shines
- Quickly adding storage for new server deployments
- Prototyping and MVP environments
- Small/midsize businesses with general IT resources
- Legacy applications using DAS
Conclusion
While NAS provides important data sharing capabilities in many environments, DAS has retain advantages in performance, reliability, security, cost, scalability and simplicity that make it a superior choice for many workload. For applications that demand speed, availability, safeguarding of sensitive data, scaling capacity without limits, and keeping costs down, DAS is hard to beat.
The optimal solution for many organizations is to utilize DAS where its strengths lie, while also employing NAS for more collaborative data that needs networked access. By selectively leveraging DAS and NAS according to use case requirements, IT can build infrastructure that is fast, robust, secure, scalable and cost-efficient.
The merits of DAS are clear for certain workloads. As NAS continues evolving, the lines may blur between these two approaches. But for now, DAS remains an indispensable access pattern for storage infrastructure. The unique advantages of directly attaching servers to storage will ensure DAS remains a critical and relevant component of the data center technology stack.