Cad iad an fáil agus an iontaoibhinn i ndearadh an chórais?

Question

Accepted Answer

**Fáil** (an córas suas agus inrochtana) agus **iontaoibhinn** (an córas ag feidhmiú i gceart) is riachtanais thábhachtacha neamh-fheidhmiúcháin iad. Bhaineann a bhaint amach le hiomadúilteacht, fhulaingt lochtanna, ag foluain pointí aonair teip, agus ag déileáil le teipthe go grasta.

## Fáil in aghaidh iontaoibhinn

```text
AVAILABILITY → the system is UP and responsive (accessible when needed):
  → measured as uptime % ("nines": 99.9% = ~8.7h/year down; 99.99% = ~52min/year)
RELIABILITY → the system works CORRECTLY (does what it should, without failures/errors):
  → related but distinct (a system can be up but returning wrong results — available but
    unreliable)
→ both matter: users need the system available AND working correctly.
```

## Fáil ard a bhaint amach

```text
✓ REDUNDANCY → multiple instances/copies → no single point of failure (if one fails,
  others serve) — the core principle
✓ Spread across AVAILABILITY ZONES / regions → survive data center/region failures
✓ FAILOVER → automatically switch to backups when something fails
✓ LOAD BALANCING + health checks → route around failed instances
✓ Database replication; eliminate SINGLE POINTS OF FAILURE everywhere
```

## Córais iontaoibhinn a thógáil

```text
✓ Design for FAILURE → assume things WILL fail; handle it gracefully (failures are normal
  at scale)
✓ FAULT TOLERANCE → continue working despite component failures (retries, fallbacks,
  circuit breakers, graceful degradation)
✓ MONITORING → detect issues; backups/recovery for data; test failure scenarios
✓ Avoid CASCADING failures (one failure triggering others) → isolation, timeouts
```

## Cén fáth a bhfuil sé tábhachtach

Tá tuiscint ar fháil agus ar iontaoibhinn bhunúsach toisc gur **riachtanais thábhachtacha neamh-fheidhmiúcháin do chórais dhíobhálacha** iad, agus dá bhrí sin is fíor-riachtanach iad a dhearadh do-bhunúsach-eolais-dheartha-chóras. **Fáil** (an córas a bheith suas agus inrochtana, tomhaiste i