Storage reliability.
WHAT TO EXPECT
Drives fail. In any substantial population, regularly.
WHAT AFFECTS FAILURE RATES
Age Temperature Vibration Workload
WHAT PATTERN FAILURES FOLLOW
Some fail early, most survive a long period, and rates rise with age.
WHAT THAT MEANS
Drives bought together tend to fail around the same time.
WHY THAT IS DANGEROUS
An array can lose a second drive while rebuilding after the first.
WHAT REDUCES THAT RISK
Arrangements tolerating two failures Prompt replacement Monitoring that gives warning
WHAT WARNING EXISTS
Drives report health indicators that frequently precede failure.
WHAT TO MONITOR
Those indicators, and act on deterioration.
WHAT HOT-SWAP MEANS
Replacing a drive without powering down.
WHY IT MATTERS
Replacement without interruption.
WHAT TO KEEP
Spare drives on hand, where response time matters.
WHAT TO DO ON FAILURE
Replace promptly, and verify the rebuild completes.
WHAT NEVER TO DO
Leave a degraded array unrepaired.
