How to Size a TrueNAS System for Your Business

Buying storage would be much easier if the number on the front of the drives told you everything you needed to know.

Unfortunately, “we need about 100TB” is usually the start of the conversation.

Is that 100TB of files you need to keep, or the total capacity of the disks? Will the system serve office documents, run virtual machines or receive overnight backups? And how much of a problem would it be if it stopped working on a busy Tuesday?

Those answers can lead to very different configurations.

This guide walks through the decisions worth making before you choose your hardware. Once you have a starting point, our TrueNAS configurator lets you explore layouts and see how your choices affect capacity.

Start with the job, then choose the box

It is tempting to start by comparing appliances. Drive bays, memory, network ports. There is plenty to get stuck into.

But start with what the system needs to do.

A backup target might need to absorb a large amount of data within a particular overnight window. Storage supporting virtual machines may need to handle lots of smaller requests throughout the day. A media team could care most about moving large files while several people work at once.

All three might need the same amount of space. That does not mean they need the same system.

Before opening a specification sheet, write down:

• What applications and people will use the storage.
• How much data you hold today, and how quickly it is growing.
• When the system will be busiest.
• How long you could manage without access to it.
• What you need to back up, and how quickly you need to recover it.

You do not need perfect answers. “We don’t know yet” is useful information too. It tells us what needs investigating before anyone orders hardware.

Why 100TB of disks is not 100TB of working space

This is where storage quotes can become confusing.

There are three different capacity figures worth understanding.

Raw capacity is the combined capacity of the installed drives. It is the biggest number, which probably explains why it gets so much attention.

Usable capacity accounts for the chosen storage layout and its overheads. Depending on that layout, some capacity goes towards redundancy rather than storing additional files.

Working capacity is the amount you plan to use while keeping some space free. Filling a storage pool to the brim leaves little room for growth or day-to-day changes.

Our configurator separates these figures. Its default planning target is 80% pool fill, and you can adjust that assumption.

You will also see TB and TiB. These measure capacity differently: drive manufacturers typically describe capacity in decimal TB, while the configurator also shows the binary TiB figure prominently.

A smaller TiB number does not mean a chunk of your storage has disappeared. It means you are looking at a different unit.

A worked example: where the capacity goes

Here is an illustrative configuration from the tool, rather than a recommendation for a particular organisation.

With eight 24TB drives, a single eight-drive RAID-Z2 group and the calculator’s default assumptions, the displayed figures were:

The calculation assumes no compression savings and uses the tool’s default 128KiB record-size assumption. Different layouts and assumptions can produce different results.

The useful lesson is the gap between the headline number and the working number. A system with 192TB of installed disks does not give you 192TB to fill with business data.

It also shows why units matter. A requirement for 100TB and a requirement for 100TiB are not quite the same brief.

Try your own capacity requirement in the TrueNAS configurator to see the breakdown for your proposed setup.

Leave room for the data you have not created yet

Your current storage usage is a starting point. The system still needs to make sense after another year of projects, backups and files that somebody is definitely going to tidy up.

Eventually.

Look at actual growth where you can. Historical storage reports are more useful than a confident guess made during a meeting.

Also account for what is changing. A new backup-retention policy, additional virtual machines or a move into video production can make last year’s growth rate a poor guide to next year.

Snapshots and retained backups need consideration too. Their space requirements depend on how much data changes and how long you keep it.

Compression may help, but the result depends on the data. Avoid building a purchase around an optimistic compression ratio that nobody has measured.

Enough space does not automatically mean enough performance

A configuration can meet your capacity requirement and still struggle with the workload.

For example, a backup system needs to complete its jobs within the available window. A system serving virtual machines needs to respond well while those machines are busy. Neither question has a complete answer in terabytes.

The network matters as well. Your storage sits within a wider setup of switches, links and client systems. A faster appliance cannot remove every bottleneck elsewhere.

This is why the configurator describes its suggested setups as capacity-led starting points. It helps you explore a valid layout from its planning catalogue. It does not benchmark your applications or promise a particular result.

Before purchasing, the workload, connectivity and final hardware specification need reviewing together.

Decide what happens when something fails

“Resilient” can mean different things to different people.

Drive redundancy addresses certain drive failures. High-availability options address a different part of the system. Backups and recovery arrangements deal with another set of problems.

They belong in the same conversation, but they do different jobs.

Ask a practical question: if this system became unavailable tomorrow morning, what would the organisation need to happen next?

That answer helps shape the availability and recovery requirements. It also stops you buying a feature simply because it sounds reassuring.

A resilient storage layout still needs a backup strategy. Deleted files, compromised accounts and site-level incidents do not politely restrict themselves to a single failed disk.

Use the configurator to make the choices clearer

You can start with hardware you already have in mind, or enter your workload and capacity requirement to find a starting setup.

From there, explore the drive layout and system options, check the capacity breakdown and compare alternatives.

Change one thing at a time. That makes it easier to understand what you gain, what you give up and which questions still need answering.

Once you have something worth discussing, save or share the configuration. It gives everyone a more useful starting point than an email saying “something around 100TB, probably”.

You do not need to arrive with a finished design. The point is to make the next conversation more specific.

A few questions worth clearing up

Can the configurator tell me exactly which system to buy?

It can help you build a starting configuration. Final compatibility, performance requirements and the complete specification still need review before quotation.

Should I choose the layout with the most usable capacity?

Only if it also meets your workload and resilience requirements. The largest capacity figure is one consideration, rather than the whole decision.

Does RAID-Z mean I do not need backups?

No. Drive redundancy helps with particular hardware failures. It does not replace a separately considered backup and recovery plan.

What if I do not know my performance requirements?

Bring what you do know: applications, users, current equipment, data volumes and the problems you are trying to solve. Identifying the missing information is part of planning the system.

Put a starting configuration together

You do not need to become a storage engineer before buying storage. You do need a clear picture of what the system must do.

Build your TrueNAS configuration, explore the capacity figures and save a setup for review.

If you would rather talk through the requirements first, our TrueNAS team at Haptic Networks can help. Call 01536 316870.

A useful starting point and a few honest questions will get the conversation moving.