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Rony_Sklar
What are key factors that businesses should take into consideration when choosing between traditional SAN and hyper-converged solutions?
author avatarTim Williams
Real User

Whether to go 3 Tier (aka SAN) or HCI boils down to asking yourself what matters the most to you:

- Customization and tuning (SAN)
- Simplicity and ease of management (HCI)
- Single number to call support (HCI)
- Opex vs Capex
- Pay-as-you-grow (HCI)/scalability
- Budget cycles

If you are a company that only gets budget once every 4/5 years, and you can't get any capital expenditures for Storage/etc, pay-as-you-grow becomes less viable, and HCI is designed with that in mind. It doesn't rule out HCI, but it does reduce some of the value gained. Likewise, if you are on a budget cycle to replace storage and compute at different times, and have no means to repurpose them, HCI is a tougher sell to upper management. HCI requires you replace both at the same time, and sometimes budgets for capital don't work out.

There are also some workloads that will work better on a 3Tier solution vs HCI and vice versa. HCI works very well for anything but VMs with very large storage footprints. One of the key aspects of HCI performance is local reads and writes, a workload that is a single large VM will require essentially 2 full HCI nodes to run, and will require more storage than compute. Video workloads come to mind for this. Bodycams for police, surveillance cameras for businesses/schools, graphic editing. Those workloads can't reduce well, and are better suited for a SAN with very few features such as an HPE MSA.

HCI runs VDI exceptionally well, and nobody should ever do 3 Tier for VDI going forward. General server virtualization can realize the value of HCI, as it radically simplifies management.

3 Tier requires complex management and time, as you have to manage the storage, the storage fabric, and the hosts separately and with different toolsets. This also leads to support issues as you will frequently see the 3 vendor support teams blame each other. With HCI, you call a single number and they support everything. You can drastically reduce your opex with HCI by simplifiying support and management. If you're planning for growth up front, and cannot pay as you grow, 3 tier will probably be cheaper. HCI gives you the opportunity to not spend capital if you end up not meeting growth projections, and to grow past planned growth much easier as adding a node is much simpler than expanding storage/networking/compute independently.

In general, it's best to start with HCI and work to disqualify it rather than the other way around.

author avatarGerman Infante
User

There are so many variables to consider.

First of all, have in mind that tendency is not the rule, your needs should be the base of decision, so you don't have to choose HCI because it's the new kid on the block.

To start, think with your pocket, SAN is high cost if you are starting the infrastructure; cables, switches, and HBAs are the components to add to this structure that have a higher cost than traditional LAN components, On the other side, SAN requires more experimented experts to manage the connections and issues, but SAN has particular benefits sharing storage and servers functions like you can have on same SAN disk and backup and use special backup software and functionalities to move data between different storage components without direct impact on servers traffic.

SAN has some details to consider on cables like distance and speed, its critical the quality or purity to get the distance; the more distance, the less speed supported and transceiver cost can be the worst nightmare. But SAN have capabilities to connect storage boxes to hundreds of miles between them, LAN cables of HCI have 100 mts limit unless you consider a WAN to connect everything or repeaters or cascaded switches adding some risk element to this scenario.

Think about required capacities, do you need TB or PB?, Some dozens of TB can be fine on HCI, But if there are PBs you think on SAN, what about availability?, several and common nodes doing replication around the world but fulfilling the rules of latency can be considered with HCI, but, if you need the highest availability, replicating and high amount of data choose a SAN.
Speed, if it is a pain in the neck, LAN for HCI starts minimum at 10 Gb and can rise up to 100 Gb if you have the money, SAN has available just up to 32 Gb and your storage controller must be the same speed, this can drive the cost to the sky.

Scalability, HCI can have dozens of nodes replicating and adding capacity, performance, and availability around the world. With SAN storage you can have a limited number of replications between storage boxes, depending on manufactures normally you can have almost 4 copies of the same volume distributed around the world and scalability goes up to controllers limits its a scale-up model. HCI is a scale-out model to grow.

Functionalities, SAN storage can manage by hardware things like deduplication, compression, multiple kinds of traffic like files, blocks or objects, , on HCI just blocks and need extra hardware to accelerate some process like dedupe.

HCI is a way to share storage on LAN and have dependencies like the hypervisor and software or hardware accelerators, SAN is the way to share storage to servers, it is like a VIP lounge, so there are exclusive server visitors to share the buffet and can share the performance of hundreds of hard drives to support the most critical response times.

author avatarManjunath V
Real User

Scalability and agility are the main consideration factor to decide between SAN and HCI. SAN infra needs huge work involvement when attaining the end of support, end of life situation. Also, budgeting and procurement frequency plays a role.

Also, the limitation of HCI to be single datastore in VMware environment is a problem, when disk corruption or data corruption happens.

author avatarShivendraJha
Real User

There are multiple factors that you shall be looking at while selecting one over the other.
1. Price- Price for HCI is cheaper if you are refreshing your complete infrastructure stack (Compute/Storage/network) however, if you are just buying individual components in the infrastructure such as compute or storage only, then 3-Tier infrastructure is cheaper.
2. Scalability-HCI is highly and easily scalable.
3. Support- On a 3 tier architecture, you have multiple vendors/departments to call/contact to get support on the solution. Whereas for HCI, you call/contact a single vendor addressing all your issues on the solution.
4. Infrastructure- For very small infrastructure, a 3Tier architecture based on iSCSI SAN can be a little cheaper. However, for a medium or large infrastructure HCI comes cheaper every time.
5. Workload type- If you are using VDI, I strongly recommend to use HCI. Similarly, for a passive secondary site, 3-tier could be OK. Please run all bench-marking tools to know what are your requirements.

I am sure HCI can do everything though.

author avatarBart Heungens
Reseller

All depends of how you understand and use HCI:
If you see HCI as an integrated solution where storage is integrated into servers, and software-defined storage is used to create a shared pool of storage across compute nodes, performance will be the game changer of choosing for HCI or traditional SAN. The HCI solution of most vendors will be writing data 2 or 3 times for redundancy across compute nodes, and so where there is a performance impact on the applications due to the latency of the network between the nodes. Putting 25Gb networks, as some vendors recommend, is not always a solution since it is npt the bandwidth nut the latency of the network that defines the performance.

Low latency application requirements might push customers to traditional SAN in this case. If you use HCO for ease of management through a single pane of glass, I see many storage vendors delivering plugins to server and application software, eliminating the need of using the legacy SAN tools to create volumes and present them to the servers. Often it is possible to create a volume directly from within the hypervisor console and attach them to the hypervisor servers. So for this scenario, I don't see a reason choosing between the one or the other.

Today there is a vendor (HPE) that is combining traditional SAN in an HCI solution calling it dHCI. It gives you a HCI user experience, the independent scalability of storage and compute, and the low latency often required. After a time I expect other vendors will follow the same path delivering these kinds of solutions as well.

author avatarKashifNaseer
Reseller

If things are working in a traditional way already and not much growth is expected then SAN is suitable. however, if things are on the cloud journey or already virtualized then HCI suites more.

author avatarJOAO BONNASSIS
User

There are two SAN (FC SAN and IP SAN), both use the SCSI v3 protocol:
- FC-SAN achieves a bandwidth of 16 and 32 Gbps.
- IP SAN achieves a bandwidth of 1, 10, and 25 Gbps.

SAN generally uses CI (Converged Infrastructure): “n” COMPUTE nodes, “n” NETWORK nodes, and “n” STORAGE nodes.

HCI (Hyper-Converged Infrastructure) uses only GbE network (1, 10, and 25 Gbps), through the SCSI V3 protocol. Each node is connected to an aggregate of nodes (Cluster – up to 64 Nodes) and have all 3 functions for each node (COMPUTE + NETWORK + STORAGE). These nodes are managed by a Hypervisor (VMware, Nutanix, ...).

If STORAGE capacity grows rapidly, HCI (Hyper-Converged Infrastructure) will not be the most suitable solution!

The two main problems are the NETWORK and the SCSI V3 protocol: high latency and limited by 25 Gbps!

author avatarSimone Gebellato
Real User

The choice is more philosophical than deterministic, it depends on what you're going to do over this new infrastructure. All the answers are excellent and I have no all these aspects on my mind, but before choosing this or that what do you need SAN or HCI for? Who is going to implement and maintain the solution?

See more Modular SAN questions »

What is Modular SAN?

When evaluating modular storage area networks, the IT Central Station users emphasized several key components. First and foremost, the SAN must be easy to integrate into the existing infrastructure and include interoperability with the different platforms it will be connecting with. In the same vein, quality modular SANs must be easy to use and manage for admins and users, and should be built with a basic interface that anyone can operate. Secondly, reliability is important, along with IOPS capacity, throughput, and flexibility to allow for spinners and flash storage capacity. Finally, good pricing was a strong concern for many of the users.

Find out what your peers are saying about Nutanix, Hewlett Packard Enterprise, Dell EMC and others in Modular SAN. Updated: August 2020.
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