Uptime is the percentage showing how much of the time the server is up. 99.9% uptime means the server may be down 8.76 hours per year (1.4 minutes per day). This is the SLA (Service Level Agreement) threshold guaranteed by hosting tariffs and services. High uptime is important for business, especially for e-commerce and mission-critical services.
Uptime percentages and their meaning
99% β 87.6 hours of downtime per year (14 minutes per day). Low, not enough for business.
99.5% β 43.8 hours per year. Still low.
99.9% ("three nines") β 8.76 hours per year. Standard professional hosting.
99.99% ("four nines") β 52 minutes per year. For premium.
99.999% ("five nines") β 5 minutes per year. Enterprise and critical systems (banks).
Factors affecting uptime
Hardware issues β disk crash, RAM errors, power supply failure. Good hosting minimizes this risk with redundancy (RAID, dual PSU).
Network issues β internet provider outage, DDoS attack, BGP routing problems.
Software issues β server software (Apache, MySQL, PHP) crash, OS update issue.
Maintenance β planned downtime for system updates (usually at night).
Uptime monitoring
Uptime Robot β free, 50 monitors, checks every 5 minutes. Pingdom β premium, checks every 1 minute from many locations. StatusCake β has a free plan too. Better Stack β modern, great alerting.
Monitoring tools check your site every 1-5 minutes and alert you via SMS, email, or Slack if it's down.
Improving uptime
CDN β Cloudflare serves static content from the edge. Cached pages still work even if the origin is down.
Load balancing β running on multiple servers. If one server goes down, others keep going.
Database replication β MySQL master-slave; if the master fails, traffic automatically shifts to the slave.
Multi-region deployment β host the site in multiple data centers. AWS Multi-AZ, Google Cloud Multi-Region.
Sayt.uz practice
Sayt.uz tariff uptime guarantees: Basic Hosting 99.9% (SLA), Pro Hosting 99.95%, Premium and VPS 99.99%. In actual 2024 numbers we delivered 99.97% uptime (total 158 minutes of downtime β mostly planned maintenance). The single biggest 2024 downtime: October 14, 47 minutes (datacenter power issue). We recommend clients monitor their sites with Uptime Robot. Tip: 99.9% uptime is the current standard β don't trust any hosting offering less.