{
  "slug": "storage-availability-correlated-failures",
  "title": "Google measured a disk MTTF of 10 to 50 years but a node MTTF of 4.3 months; 37% of node failures came in bursts",
  "kind": "dataset",
  "summary": "Ford et al., OSDI 2010, studied tens of Google storage cells over one year. Node MTTF was 4.3 months against 10 to 50 years for a disk, and 37% of failures were part of a burst of at least 2 nodes. Cross-check rows come from NetApp (FAST 2020) and HPC1 (FAST 2007) and show clustered drive replacements.",
  "license": "Small derived table of figures printed in Ford et al. (OSDI 2010), Maneas et al. (FAST 2020), and Schroeder and Gibson (FAST 2007), with credit. Not a Creative Commons license. The USENIX papers remain with their authors or publishers. This file is not a copy of the papers and not the data.",
  "licenseUrl": "https://www.usenix.org/legacy/event/osdi10/tech/full_papers/Ford.pdf",
  "sourceUrl": "https://www.usenix.org/legacy/event/osdi10/tech/full_papers/Ford.pdf",
  "accessed": "2026-10-10",
  "rowCount": 14,
  "columns": [
    {
      "name": "measure",
      "type": "string",
      "description": "The quantity as the source names it."
    },
    {
      "name": "value_low",
      "type": "number",
      "description": "Lower end of a printed range. Empty when the source prints a single value."
    },
    {
      "name": "value_high",
      "type": "number",
      "description": "Single printed value, or the upper end of a range. For 'less than' it is the stated bound."
    },
    {
      "name": "unit",
      "type": "string",
      "description": "Unit of the value columns: nodes per cell, percent, years, months, fraction, times, or correlation coefficient."
    },
    {
      "name": "scope",
      "type": "string",
      "description": "Population and window the value applies to."
    },
    {
      "name": "note",
      "type": "string",
      "description": "What the value is not, or the source wording behind it."
    },
    {
      "name": "citation_id",
      "type": "string",
      "description": "Id of the opened source in the citations list."
    }
  ],
  "downloadPath": "/data/datasets/storage-availability-correlated-failures.csv",
  "humanPage": "https://hesela.com/analyses/storage-availability-correlated-failures/",
  "limits": [
    "One operator's cells and software; figures describe nodes and racks as well as disks.",
    "Disk MTTF is a printed range of 10 to 50 years, not a vendor rating.",
    "The 10% sensitivity results come from the authors' model with 3-way replication.",
    "The 37% burst share depends on a 120 second window.",
    "The cross-check rows are other fleets with other definitions."
  ],
  "citations": [
    {
      "id": "ford-osdi10-pdf",
      "title": "Availability in Globally Distributed Storage Systems, Ford, Labelle, Popovici, Stokely, Truong, Barroso, Grimes, and Quinlan, USENIX OSDI 2010 (USENIX PDF)",
      "url": "https://www.usenix.org/legacy/event/osdi10/tech/full_papers/Ford.pdf",
      "accessed": "2026-10-10"
    },
    {
      "id": "maneas-fast20-pdf",
      "title": "A Study of SSD Reliability in Large Scale Enterprise Storage Deployments, Maneas, Mahdaviani, Emami, and Schroeder, FAST 2020 (USENIX PDF, section 6 on correlated replacements)",
      "url": "https://www.usenix.org/system/files/fast20-maneas.pdf",
      "accessed": "2026-10-10"
    },
    {
      "id": "schroeder-fast07-pdf",
      "title": "Disk failures in the real world: What does an MTTF of 1,000,000 hours mean to you?, Schroeder and Gibson, FAST 2007 (USENIX PDF, section 5.2 on correlations)",
      "url": "https://www.usenix.org/legacy/events/fast07/tech/schroeder/schroeder.pdf",
      "accessed": "2026-10-10"
    }
  ]
}