Don’t Let Your Network Bottleneck Your Hyperconverged Storage
Hyperconverged infrastructure (HCI) promises simplicity and speed—but many deployments fall short under pressure. Without the right network design, microbursts during events like rebuilds or live migrations cripple performance. Deep-buffered Ethernet fabrics prevent these slowdowns, protecting your investment and ensuring your applications run reliably at scale.
Why Deep Buffers Matter for HCI
Handles East-West Traffic Bursts
HCI generates unpredictable traffic spikes between nodes. Deep buffers absorb these surges without dropping packets.
Prevents Latency Spikes
Dropped packets force costly retransmissions, turning microsecond latency into milliseconds. Deep buffers keep data flowing smoothly.
Avoids Costly Downtime
During rebuilds or live migrations, shallow buffers can stall workloads. Deep buffers ensure continuity for business-critical apps.
Maximizes ROI on All-Flash Storage
Flash storage is fast—but only if the network can keep up. Deep buffers ensure your high-performance hardware delivers consistent results..
Why Standard Networks Fall Short for HCI
Modern HCI has transformed how enterprises deploy storage. Instead of a traditional SAN where traffic flows to a central array (north-south), HCI creates intense east-west traffic between nodes. During normal operations, this traffic is manageable—but certain events create sudden spikes:
Node Rebuilds: After a node failure, surviving nodes must rapidly rebuild data on replacement hardware. This triggers high-volume “many-to-one” data flows to a single switch port.
Mass VM Migrations: Maintenance windows or load balancing can involve dozens of VMs moving at once, hammering the network.
Cluster-Wide Backups or Snapshots: Large-scale backups generate synchronized bursts of traffic from every node in the cluster.
Traditional data center switches cannot handle these bursts. They’re designed for traditional data center workloads and not the sustained data flows of s hyperconverged cluster under load.
The tables below compare typical deep buffer (Arista solutions) and commodity DC switching solutions offered to Nutanix users when planning for Nutanix deployments, the mismatch in approaches is readily apparent, with Arista typically 100x deeper in buffer scale than Cisco and Juniper solutions. The elimination of microburst driven discards is a significant driver of better availability and performance in HCI environments running on Arista 7200R3 series.
Table: Deep Buffer vs Shallow Buffer Switches (typical 48x 25GB HCI ToR)
| Feature / Specification | Arista (DCS-7280SR3-48YC6) | Cisco Nexus 93180YC-FX3 | Juniper QFX5120-48Y |
| Ports | 48 x 10/25G + 6 x 100G | 48 x 25G + 6 x 100G | 48 x 25G + 8 x 100G |
| Buffer Memory (Total) | 4GB Shared (100x deeper) | ~ 40MB Shared | ~ 32MB Shared |
| Buffer Type | Deep shared dynamic pool | Shallow shared pool | Shallow shared pool |
| Total Switching Capacity | 3.6Tbps | 3.6Tbps | 3.6Tbps |
| Ideal Use Case | Standard Nutanix clusters with moderate east-west traffic, all other DC use cases except high-density spine | Data center edge, general compute, moderate HCI deployments | Data center edge, general compute, moderate HCI deployments |
| Latency Profile | Low, optimized for microbursts | Low, but susceptible to microbursts | Low, but susceptible to microbursts |
| RoCE/PFC Support | Yes | Yes | Yes |
| Power Draw | ~ 600-850W | ~ 500-700W | ~ 300-450W |
| OS / OS Quality | Arista EOS | | Nexus OS | | JunOs | |
| Observability/Telemetry | CloudVision, Tracer Integration with Nutanix AHV | Streaming telemetry but less Nutanix-specific integration | Streaming telemetry but less Nutanix-specific integration |
Table: Deep Buffer vs Shallow Buffer Switches (High Performance/High Density 32 x 100GB HCI ToR)
| Feature / Specification | Arista DCS-7280CR3-32P4 | Cisco Nexus 9336C-FX2 | Juniper QFX5200-32C |
| Ports | 32 x QSFP100, 4 x 400G | 36 x 100G | 32 x 100G |
| Buffer Memory (Total) | 8GB Shared (100x deeper) | ~40MB | ~16MB |
| Buffer Type | Deep shared dynamic pool | Shallow shared pool | Shallow shared pool |
| Total Switching Capacity | 9.6Tbps | 7.2Tbps | 6.4Tbps |
| Ideal Use Case | High-density, high-performance HCI, High-speed spines | High-speed spines, low performance HCI at density | High-speed spines, low performance HCI at density |
| Latency Profile | Low, optimized for microbursts | Low, but susceptible to microbursts | Low, but susceptible to microbursts |
| RoCE/PFC Support | Yes | Yes | Yes |
| Power Draw | ~ 500-750W | ~ 700-800W | ~ 650-950W |
| OS / OS Quality | Arista EOS | | Nexus OS | | JunOS | |
| Observability/Telemetry | CloudVision, Tracer Integration with Nutanix AHV | Streaming telemetry but less Nutanix-specific integration | Streaming telemetry but less Nutanix-specific integration |
The Real Cost of Dropped Packets
Dropped packets in a storage environment are far more than minor inconveniences. Here’s what happens:
1. A burst of traffic arrives faster than a shallow buffer can forward it.
2. Packets overflow and are dropped.
3. TCP waits for a timeout, then retransmits.
4. Latency jumps from microseconds → milliseconds.
5. Application performance tanks, even on fast flash storage.
A single dropped packet can delay an I/O by hundreds or thousands of microseconds. Multiply that by thousands of lost packets during a cluster rebuild, and your all-flash storage grinds to a halt.
When Deep Buffers Save Your HCI Deployment
Scenarios where deep buffers are critical:
Node Failures and Rebuilds: Without deep buffers, rebuild traffic overwhelms shallow switches, causing performance drops that ripple across your apps.
Mass VM Migrations: Moving dozens of VMs can saturate switch ports. Deep buffers keep performance steady even during peak migrations.
Backup Storms: Scheduled backups or snapshots generate synchronized bursts. Deep buffers absorb these without packet loss.
All-Flash Storage Environments: Flash delivers microsecond latency—but it’s wasted if the network introduces millisecond delays due to dropped packets.
How to Choose the Right Network for HCI
For enterprises running Nutanix, VMware, or other HCI platforms, the choice of network gear makes the difference between seamless performance and chronic slowdowns.
Recommendations:
Invest in Deep Buffers: Look for switches measured in MB or GB of shared buffer space, like the Arista 7280R3 or 7500R3.
Ensure Lossless Ethernet Support: Combine deep buffers with Priority Flow Control (PFC) and ECN to eliminate packet loss.
Plan for Future Workloads: HCI demands will only increase. Ensure your network can handle 100G, 400G, and beyond.
Frequently Asked Questions
Why do hyperconverged infrastructures (HCI) need deep-buffer switches?
Because HCI generates intense bursts of east-west traffic—especially during events like node rebuilds, VM migrations, or backups. Shallow-buffer switches can’t absorb these microbursts, leading to dropped packets, retransmissions, and severe performance degradation. Deep buffers act as a shock absorber, protecting your storage traffic and ensuring consistent latency and throughput.
Isn’t all-flash storage fast enough to avoid these problems?
No. Flash eliminates disk latency but can’t fix network congestion. Even in an all-flash HCI, storage traffic still has to traverse the network. When that network can’t handle microbursts, the flash array sits idle waiting for retransmissions. Deep-buffered switches ensure that your fast storage isn’t held hostage by network bottlenecks.
How much deeper are Arista’s buffers compared to typical data center switches?
Many campus or generic data center switches have total buffers measured in tens of megabytes. Arista’s deep-buffer models (like the 7280SR3 series) offer 4GB or more—over 100 times deeper than a typical 40MB buffer in many competing switches. This is crucial for preventing packet drops during large east-west surges in HCI environments.
Does deep buffering impact latency?
Not in a negative way. Deep buffers don’t inherently increase latency. They only come into play when a burst threatens to overrun the switch’s forwarding capacity. Instead of dropping packets, the buffer holds them briefly until congestion clears, preserving performance rather than harming it.
Can’t we just avoid microbursts by spreading out workloads?
You can reduce the frequency of microbursts with careful workload placement, but you can’t eliminate them. HCI clusters are dynamic. Events like node rebuilds or mass migrations can cause sudden, unavoidable bursts. Deep buffers ensure your network is resilient even when bursts happen.
Are deep-buffer switches only for large environments?
Not at all. Even smaller HCI clusters can generate bursty traffic patterns that overwhelm shallow buffers. While the problem grows as your cluster scales, deep buffers are valuable protection for any serious production HCI deployment.
Is there a difference between deep buffers and just buying higher-speed switches?
Yes. Speed alone isn’t the answer. A faster switch port (e.g. 100G) can still suffer packet drops if it can’t absorb short-term spikes in traffic. Deep buffers and high speed work together—speed provides bandwidth, while buffers protect you during unpredictable bursts.
Are deep buffers only relevant for Nutanix?
No. Deep buffers matter in any hyperconverged or scale-out environment—Nutanix, VMware vSAN, Microsoft Azure Stack HCI, or any distributed system where multiple nodes replicate data across the fabric. It’s a fundamental network design requirement, not a vendor-specific feature.
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