Demystifying RAID 1 vs RAID 5: Which Should You Choose?

Thanks for reading this comparison between two of the most popular RAID options for improving storage performance and redundancy – RAID 1 and RAID 5.

In this piece, we are going to unravel the mystery of when to pick mirroring through RAID 1 versus striping with distributed parity in RAID 5. Our journey will explore the technical architecture that allows these RAIDS to boost resilience and availability. We’ll also run through various examples so you can truly grasp which works best for common situations from media servers to databases.

Buckle up – it’s time to make sense of it all!

A Quick Intro to RAID Storage

Before diving deep on RAID 1 versus 5 specifically, let’s quickly recap RAID (Redundant Array of Independent Disks)…

RAID combines multiple disk drives together into a logical unit. Different RAID “levels” then arrange the data across the drives uniquely to deliver increased capacity, speed, redundancy or a combo.

Some famous RAID level highlights:

• RAID 0 – Striping to multiply speed
• RAID 1 – Mirroring for live redundancy
• RAID 5 – Distributed parity stripes
• RAID 6 – Double parity for extra resilience

When planning any storage system, one of the first questions is: do I optimize for maximum speed, redundancy or capacity? Your answer guides you towards selecting a suitable RAID level.

By design, RAID 1 favors availability and RAID 5 favors storage size. Now let’s explore exactly why…

Inside RAID 1: Split-Second Mirror Synchronization

At the core of RAID 1 is duplicating your data onto additional disks continuously and in real-time. This “mirroring” ensures an exact copy exists across multiple drives simultaneously.

For example, with a 2-drive RAID 1 array, whenever data is written to the primary disk, the RAID controller also writes the same data to the second “mirror” disk. This happens instantly behind-the-scenes through the synchronization process.

The magic behind this mirroring is the RAID controller coordinating the data duplication. This manages splitting inbound writes to go to both disks plus reconciling if reads happen from just one. Some controller caching also helps accelerate read performance.

If either mirrored drive fails, the controller simply redirects all activity to the surviving drive containing an intact copy of the data. This failover happens seamlessly allowing zero downtime in most cases.

Once replaced, the failed drive gets added back to the RAID 1 array. The controller automatically re-mirrors all the existing data to bring consistency across disks. This “rebuild” process occurs in the background with minimal performance impact.

In this manner, RAID 1 grants tremendous resilience advantages. The real-time synchronized copies onboard other disks enable continuous operations even with physical drive failures. This makes RAID 1 the go-to for maximizing availability in mission critical systems.

However, RAID 1 incurs a big capacity sacrifice…

The usable storage of a RAID 1 array only ever equals a single disk drive. Adding more mirror drives simply creates additional copies – so you gain more redundancy but not more net capacity. For storage-hungry applications, RAID 1 can become expensive needing ever larger drives.

Now how does RAID 5 achieve high capacity plus redundancy? With some parity magic…

Inside RAID 5: Spreading Parity Protection

Unlike RAID 1 copying entire drive contents, RAID 5 distributes data across all the drives at the block level. It also designates parity blocks to enable recovering data if a disk fails.

For example, in a 3-disk RAID 5 array, data gets spread around filling up Blocks 1-5 in Disks 1-3 as shown below. The parity data resides in Disk 3 allowing any single disk failure recovery:

If Disk 2 died here, the parity block on Disk 3 has enough information to reconstruct the missing Block 3. By calculating parity from the remaining data on Disk 1, the RAID controller can infer what data is needed to satisfy the parity check.

This style of parity protection provides single disk fault tolerance. But it comes at the cost of slower write speeds…

Because data is spread out in chunks rather than mirrored entirely, any incoming writes trigger multiple operations:

1. Old data block is read to calculate current parity
2. Updated data block gets written to new location
3. Parity gets updated across the disks

This multi-step shortcoming really slows down write-heavy workloads on RAID 5. Databases requiring many small random writes can crawl compared to RAID 1 simple mirroring.

However, on reads, RAID 5 achieves blazing fast speeds thanks to parallel access across drives – perfect for media streaming! Plus you effectively gain the capacity of all disks minus one instead of just a single disk like mirrored RAID.

Clearly RAID 5 strikes an ingenious balance between performance, protection and storage efficiency.

Now that we’ve highlighted the core differences, let’s compare some measurable metrics side-by-side…

RAID 1 vs RAID 5: Speed, Capacity and Cost Comparison

Source: StorageReview Test Lab Benchmarks

Based on performance characteristics alone, we can conclude:

• RAID 1 reads modestly faster than a single drive while writes remain similar thanks to continuous mirroring
• RAID 5 achieves exponentially better read speeds from striping but writes much slower due to parity calculations
• RAID 5 gives far higher usable capacity thanks to storage efficiency
• RAID 1 costs more per TB since we “lose” capacity from the mirrors

Now that we can quantify the differences, how does this guide our real-world system architectures…

When Should I Use RAID 1 or RAID 5?

With all trade-offs considered, here are some common scenarios that suit RAID 1 and RAID 5 storage:

RAID 1 Use Cases

• Database Servers – Mirroring delivers constant uptime during disk rebuilds. Faster writes help OLTP databases too.
• Hyperconverged Infrastructure – Combined compute and storage favors redundancy.
• Virtual Desktop Infrastructure (VDI) – Many running VMs mandate always-on availability.
• CRM / ERP Systems – Important apps and data protected.

RAID 5 Use Cases

• Media Streaming Servers – Massive capacity for media files paired with fast scrubbing capability.
• File Servers – Optimized for storage size and throughput for bulk files.
• Backup Servers – Affordable capacity and I/O for backups.
• Affordable Archival – Lower cost per TB allows massive archiving.

We can make three key conclusions from the representative use cases:

1. Transactional apps needing round-the-clock availability – Use RAID 1
2. Content repositories focused on capacity – Go for RAID 5
3. General enterprise apps – RAID 5 offers more bang for buck

For maximum performance AND protection combine them with RAID 10!

The Best of Both Worlds: RAID 10

An alternative solution giving us lightning fast mirroring WITH efficient striped capacity is the aptly named RAID 10.

RAID 10 combines both RAID 1 mirroring and RAID 0 striping together:

It works by first making mirrored pairs of drives using RAID 1. We then stripe data across each RAID 1 mirrored set using techniques from RAID 0.

The result? RAID 10 serves up excellent read AND write speeds perfect for IO hungry databases. Yet still grants a safety net against physical drive failures too!

While more costly than solo RAID 1 or RAID 5, pairing mirroring with striping creates one of the highest performance and most reliable architectures money can buy.

If you demand uncompromising speed AND resilience, consider investing in RAID 10 rather than debating RAID 1 vs 5 tradeoffs.

Making Your RAID 1 vs RAID 5 Decision

Deciding between RAID levels ultimately comes down to understanding your specific needs concerning redundancy, performance and capacity.

As we covered together, both RAID 1 and RAID 5 have well-defined strengths making each ideal for different scenarios.

• Seek maximum availability and protection? Choose RAID 1 mirroring.

• Want high capacity plus solid mixed workload throughput? Go with RAID 5 parity.

• Require uncompromising performance AND redundancy? Select RAID 10 hybrid approach.

Thank you for sticking through this journey contrasting RAID 1 and 5 side-by-side. Hopefully the full technology breakdown, metrics and use case examples provide clarity picking the right RAID for YOUR requirements.

Please drop me any follow up questions in the comments section below!