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Hot vs warm vs cold storage: how to tier your data for cost and performance

Not all data needs the same storage performance. Tiering puts frequently accessed data on fast, expensive media (NVMe SSDs) and rarely accessed data on slow, cheap media (HDDs, tape, cloud archival). Getting this right saves money without sacrificing performance. Getting it wrong means either overspending on flash you don't need or making users wait for data that should be hot.

Hardware tier
Storage
Persistent storage devices
Topic focus
Storage tier guide
storage-tiers

How this is calculated

Hot tier: NVMe SSD, data accessed multiple times per day. Database primary storage, active project files, container images. Warm tier: HDD or S3 Standard, data accessed weekly to monthly. Older logs, completed project archives, backup sets less than 30 days old. Cold tier: S3 Glacier or LTO tape, data accessed yearly or less. Compliance archives, raw data from completed research projects, backups older than 90 days. The latency difference between hot and cold can be 100,000x (100 µs vs 10+ seconds for retrieval from deep archive). Cloud providers automate tiering with lifecycle policies. On-premises, tools like automatic storage tiering in ZFS and Storage Spaces do the same.

Verdict

Tier your storage. Keep hot data on NVMe, warm data on HDD or cheap object storage, and cold data in archival. The cost difference between NVMe and archival is roughly 50-100x per GB. For a 100 TB dataset, correct tiering can save thousands per month.

More Latency scenarios

L1 vs L2 cache
l1-vs-l2
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L3 cache vs RAM
l3-vs-ram
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DDR4 vs DDR5 latency
ddr4-vs-ddr5
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NVMe vs SATA SSD
nvme-vs-sata
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SSD vs HDD speed
ssd-vs-hdd
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CPU cache hierarchy
cache-hierarchy
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Memory latency numbers
latency-numbers
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Optane vs NAND
optane-vs-nand
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RAM disk vs NVMe
ramdisk-vs-nvme
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PCIe 4.0 vs 5.0 SSDs
pcie-gen4-vs-gen5
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Frequently asked questions

How much faster is L1 cache than RAM?
Roughly 40-60x faster for random access. L1 cache access is about 1 ns; DDR5 RAM is about 50-80 ns end-to-end including controller overhead. That's why keeping hot data in cache dominates real-world CPU performance.
Is NVMe SSD faster than RAM?
No. NVMe is fast for storage, but for random access its latency is around 50-150 µs versus RAM's 50-80 ns. That's a 1,000x gap. NVMe beats RAM only on raw capacity and persistence, never on latency.
Why is HDD so much slower than SSD?
A spinning HDD has to physically move a read head to the right track and wait for the platter to rotate into position, typically 5-15 ms per random access. An SSD has no moving parts and returns data in under 100 µs, roughly 100x faster for random reads.
What's the point of L3 cache?
L1 and L2 are tiny (KB to low MB) and per-core. L3 is much larger (tens of MB) and shared across cores, acting as a buffer before requests go to main RAM. It catches data evicted from L1/L2 and data shared between cores.
How many nanoseconds is one CPU cycle?
At 4 GHz, one cycle is 0.25 ns. At 5 GHz, 0.2 ns. Cache hits are measured in single-digit cycles; main memory access costs hundreds of cycles, which is why optimizing for cache locality matters enormously in performance-critical code.
Does DDR5 have lower latency than DDR4?
Not usually at the same relative tier. DDR5 improved bandwidth and capacity significantly, but true latency (in ns) for mainstream kits is similar to late-stage DDR4. The gains from DDR5 come from bandwidth and larger capacities, not lower memory latency.

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