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EBS Volume Types: gp3 vs io2 vs st1 vs sc1 - When to Use What?

Compare AWS EBS volume types (gp3, gp2, io2, io1, st1, sc1) by performance, cost, and use cases. Learn optimal volume selection criteria for SAA-C03 exam.

PHILOLAMB••-•Updated: January 31, 2026
EBSgp3io2st1sc1Storage

Related Exam Domains

  • Domain 3: Design High-Performing Architectures
  • Domain 4: Design Cost-Optimized Architectures

Key Takeaway: EBS Volume Type Selection

For most workloads, gp3 is sufficient. Choose io2 for 16,000+ IOPS or sub-millisecond latency, st1 for high-throughput sequential processing, and sc1 for minimum cost cold data.

Comparison at a Glance

Volume TypeMax IOPSMax ThroughputLatencyIdeal Workload
gp316,0001,000 MB/sMillisecondsGeneral purpose, boot volumes, dev/test
io2256,0004,000 MB/sSub-millisecondHigh-performance DB, SAP HANA
st1500500 MB/s-Big data, log processing
sc1250250 MB/s-Cold data, archive

Exam Tip

Exam Essential: "General purpose/boot volume" → gp3, "High-performance DB/SAP HANA" → io2, "Big data/throughput" → st1, "Lowest cost/cold data" → sc1

EBS Volume Type Categories

EBS volumes are divided into SSD-based and HDD-based types.

┌─────────────────────────────────────────────────────────────┐
│                    EBS Volume Types                          │
├──────────────────────────┬──────────────────────────────────┤
│       SSD-based          │           HDD-based              │
│   (Random I/O optimized) │     (Sequential I/O optimized)   │
├──────────────────────────┼──────────────────────────────────┤
│  ┌────────┐ ┌────────┐   │   ┌────────┐  ┌────────┐        │
│  │  gp3   │ │  io2   │   │   │  st1   │  │  sc1   │        │
│  │General │ │ High   │   │   │Through-│  │ Cold   │        │
│  │Purpose │ │Perform.│   │   │  put   │  │        │        │
│  └────────┘ └────────┘   │   └────────┘  └────────┘        │
│                          │                                  │
│  • Boot volume support   │   • No boot volume support       │
│  • Random read/write     │   • Sequential read/write        │
│  • Low latency           │   • High throughput              │
└──────────────────────────┴──────────────────────────────────┘

SSD Volumes: gp3 vs gp2 vs io2 vs io1

Most cost-effective general-purpose SSD, suitable for most workloads.

gp3 Performance Model
┌─────────────────────────────────────────────────────┐
│                                                     │
│  Baseline Performance (Free)                        │
│  ┌─────────────────────────────────────┐            │
│  │ 3,000 IOPS + 125 MB/s              │            │
│  └─────────────────────────────────────┘            │
│                                                     │
│  Additional Performance (Paid)                      │
│  ┌─────────────────────────────────────┐            │
│  │ Up to 16,000 IOPS + 1,000 MB/s     │            │
│  └─────────────────────────────────────┘            │
│                                                     │
│  IOPS and throughput can be set independently       │
└─────────────────────────────────────────────────────┘
SpecValue
Volume Size1 GiB – 16 TiB
Baseline IOPS3,000 (free)
Max IOPS16,000
Baseline Throughput125 MB/s (free)
Max Throughput1,000 MB/s
LatencySingle-digit milliseconds
Durability99.8–99.9%

gp3 vs gp2 Comparison

Aspectgp3gp2
Price$0.08/GB$0.10/GB
Baseline IOPS3,000 (fixed)100–3,000 (size-based)
IOPS ConfigIndependentTied to volume size
Throughput ConfigIndependentTied to volume size
BurstNone (consistent performance)Yes (credit depletion possible)

Exam Tip

Migrate gp2 to gp3: gp3 is 20% cheaper at the same performance and allows independent IOPS/throughput configuration for more flexibility.

gp3 Suitable Workloads:

  • Boot volumes
  • Development and test environments
  • Medium-sized single-instance databases
  • Virtual desktops
  • Most transactional workloads

io2 Block Express: Provisioned IOPS SSD

Highest performance EBS volume for mission-critical workloads.

io2 Block Express Performance
┌─────────────────────────────────────────────────────┐
│                                                     │
│  ┌─────────────────────────────────────┐            │
│  │ Up to 256,000 IOPS                 │            │
│  │ Up to 4,000 MB/s throughput        │            │
│  │ Average latency under 500μs        │            │
│  │ 99.999% durability                 │            │
│  └─────────────────────────────────────┘            │
│                                                     │
│  IOPS:GB ratio = up to 1,000:1                     │
│  (1,000GB volume → up to 1,000,000 IOPS requested) │
│  (Actual max capped at 256,000 IOPS)              │
└─────────────────────────────────────────────────────┘
SpecValue
Volume Size4 GiB – 64 TiB
Max IOPS256,000
Max Throughput4,000 MB/s
LatencyUnder 500μs (sub-millisecond)
Durability99.999% (100x better than io1)
Multi-AttachSupported

io2 vs io1 Comparison

Aspectio2 Block Expressio1
Max IOPS256,00064,000
Max Throughput4,000 MB/s1,000 MB/s
Durability99.999%99.8–99.9%
IOPS:GB Ratio1,000:150:1
LatencyUnder 500μsMilliseconds

io2 Suitable Workloads:

  • SAP HANA
  • Microsoft SQL Server (high-performance)
  • Oracle Database (mission-critical)
  • MongoDB, Cassandra (high-performance)
  • I/O-intensive NoSQL databases

Exam Tip

When to Choose io2: When gp3's 16,000 IOPS isn't enough, sub-millisecond latency is required, or 99.999% durability is needed

HDD Volumes: st1 vs sc1

HDD volumes are optimized for sequential large I/O.

st1: Throughput Optimized HDD

Low-cost HDD optimized for large sequential workloads.

st1 Performance Model (Burst)
┌─────────────────────────────────────────────────────┐
│                                                     │
│  Baseline throughput: 40 MB/s per TiB              │
│  Burst throughput: 250 MB/s per TiB                │
│  Max throughput: 500 MB/s                          │
│                                                     │
│  Burst Credits                                     │
│  ████████████████░░░░░░░░░░░░░░░░  50%             │
│                                                     │
│  • High throughput when burst credits available    │
│  • Throttled to baseline when credits depleted     │
└─────────────────────────────────────────────────────┘
SpecValue
Volume Size125 GiB – 16 TiB
Max IOPS500
Baseline Throughput40 MB/s per TiB
Burst Throughput250 MB/s per TiB
Max Throughput500 MB/s
Boot VolumeNot supported

st1 Suitable Workloads:

  • Apache Kafka
  • Big data (MapReduce, Spark)
  • Data warehouses
  • Log processing
  • ETL workloads

sc1: Cold HDD

Lowest cost EBS volume for infrequently accessed data.

SpecValue
Volume Size125 GiB – 16 TiB
Max IOPS250
Baseline Throughput12 MB/s per TiB
Burst Throughput80 MB/s per TiB
Max Throughput250 MB/s
Boot VolumeNot supported

sc1 Suitable Workloads:

  • Cold data storage
  • Infrequently accessed archives
  • Backup data
  • Cost optimization as top priority

st1 vs sc1 Comparison

Aspectst1sc1
PurposeThroughput-focusedCost-focused
Baseline Throughput40 MB/s per TiB12 MB/s per TiB
Burst Throughput250 MB/s per TiB80 MB/s per TiB
Max Throughput500 MB/s250 MB/s
PriceHigherLowest

Exam Tip

HDD Selection Criteria: Choose st1 for throughput, sc1 for cost. If random I/O is frequent, choose SSD (gp3) instead of HDD.

Volume Type Selection Guide

Decision Flowchart

Is it a boot volume?
    │
    ├── Yes ──► gp3 (only SSD supports boot volumes)
    │
    └── No ──► What's the workload pattern?
                  │
                  ├── Random I/O ──► Need more than 16,000 IOPS?
                  │                    │
                  │                    ├── Yes ──► io2
                  │                    │
                  │                    └── No ──► gp3
                  │
                  └── Sequential I/O ──► Is throughput important?
                                          │
                                          ├── Yes ──► st1
                                          │
                                          └── No ──► sc1
WorkloadRecommendedReason
EC2 boot volumegp3General purpose, fast boot
Dev/Testgp3Cost-effective
Web servergp3Typical I/O patterns
Small/medium DBgp3Sufficient IOPS
High-performance OLTPio2High IOPS, low latency
SAP HANAio2Sub-millisecond latency required
Big data/Kafkast1High throughput
Log processingst1Sequential write optimized
Archivesc1Lowest cost

Cost Optimization

Pricing by Volume Type (us-east-1)

Volume TypePrice per GBIOPS PriceThroughput Price
gp3$0.08$0.005/IOPS (over 3,000)$0.04/MB/s (over 125)
gp2$0.10IncludedIncluded
io2$0.125$0.065/IOPSIncluded
io1$0.125$0.065/IOPSIncluded
st1$0.045IncludedIncluded
sc1$0.015IncludedIncluded

Cost Reduction Strategies

  1. Migrate gp2 to gp3

    • 20% cost savings at same performance
    • Just change volume type (no downtime)

  2. Consider gp3 instead of io1/io2

    • Up to 87% savings for 16,000 IOPS or less
    • Example: io2 $582.50/month → gp3 $80/month (same performance)

  3. Leverage HDD

    • Use st1/sc1 for sequential I/O workloads
    • Maximum savings with sc1 for cold data

  4. Right-size volumes

    • Monitor utilization and eliminate over-provisioning
    • Use CloudWatch EBS metrics

SAA-C03 Exam Focus Points

Common Question Types

  1. General workload volume selection

    • Answer: gp3
    • Hints: "boot volume", "dev/test", "cost-effective"

  2. High-performance database volume

    • Answer: io2
    • Hints: "SAP HANA", "mission-critical", "sub-millisecond"

  3. Big data/throughput workloads

    • Answer: st1
    • Hints: "Kafka", "MapReduce", "log processing", "large sequential"

  4. Lowest cost storage

    • Answer: sc1
    • Hints: "infrequently accessed", "archive", "minimize cost"

  5. gp2 vs gp3 comparison

    • Answer: gp3 is cheaper and more flexible
    • "Burst credit depletion" issue → solved by gp3

Exam Tip

Sample Exam Question: "A company processes large datasets sequentially for big data analytics. They need cost-effective storage with high throughput. Which EBS volume type should they use?"

→ Answer: st1 (Throughput Optimized HDD, optimal for sequential I/O)

Key Memorization Points

KeywordAssociation
Boot volumegp3 (SSD only)
General purpose, dev/testgp3
Burst credit issuesgp2 → migrate to gp3
Over 16,000 IOPSio2
Sub-millisecond latencyio2
SAP HANAio2
Big data, Kafkast1
Log processing, ETLst1
Cold data, archivesc1
Lowest costsc1

FAQ

Q1: Should I use gp2 or gp3?

Recommend gp3. gp3 is 20% cheaper at the same performance and allows independent IOPS/throughput configuration. gp2 is considered a legacy volume.

Q2: When do I need io2?

io2 is needed when:

  • More than 16,000 IOPS required
  • Sub-millisecond (under 500μs) latency needed
  • 99.999% durability required
  • SAP HANA, mission-critical databases

Q3: When should I use HDD volumes (st1, sc1)?

For sequential large I/O workloads. If random I/O is frequent, SSD (gp3) is more suitable than HDD.

  • st1: Big data, Kafka, log processing (throughput priority)
  • sc1: Cold data, archive (cost priority)

Q4: Can I change volume types?

Yes. With Elastic Volumes, you can change volume type, size, and IOPS without downtime. However, there are some limitations when switching between HDD↔SSD.

Q5: What is Multi-Attach?

Multi-Attach allows an io2/io1 volume to be attached to multiple EC2 instances in the same AZ simultaneously. Useful for cluster applications, but requires application-level write coordination.

Summary

The key to EBS volume selection is choosing the right type for your workload pattern:

  1. Most workloads: gp3 (general purpose, cost-effective)
  2. High-performance databases: io2 (maximum performance, low latency)
  3. Big data/sequential processing: st1 (high throughput)
  4. Cold data: sc1 (lowest cost)

SAA-C03 exam frequently tests selecting the right volume type based on workload characteristics. Watch for keywords like "boot volume", "SAP HANA", "big data", and "lowest cost".