Every nine costs 10×

Each extra "nine" of uptime — 99% → 99.9% → 99.99% — costs roughly an order of magnitude more effort.

Why it works

99% allows 3.7 days of downtime a year; 99.99% allows 52 minutes. Chasing nines past what users notice is expensive vanity.

More in Computers

• 2¹⁰ ≈ 10³Every 10 bits multiplies by ~1,000 — kibi and kilo differ by just 2.4%.
• Each subnet bit halves the hostsEvery bit moved from host to network halves the addresses — a /24 has 254 usable.
• RAID is not a backupRAID protects against disk failure — deletion, ransomware and fat fingers replicate instantly.
• 3-2-1 backupsKeep 3 copies of anything that matters, on 2 different media, with 1 off-site.

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