Apa iku ketersediaan lan keandalan ing desain sistem?

Question

Accepted Answer

**Ketersediaan** (sistem isih urip lan bisa diakses) lan **keandalan** (sistem berfungsi kanthi bener) iku syarat non-fungsional sing penting. Entuk maneh durung mbutuhake redundansi, toleransi kegagalan, ngilang titik kegagalan tunggal, lan nangani kegagalan kanthi apik.

## Ketersediaan vs keandalan

```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.
```

## Raih ketersediaan dhuwur

```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
```

## Bangun sistem sing andal

```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
```

## Mengapa penting

Paham ketersediaan lan keandalan iku dhasar amarga iku **syarat non-fungsional kunci kanggo sistem produksi**, dadi desain kanggo raih maneh iku kawruh sistem-desain sing penting. **Ketersediaan** (sistem isih urip lan bisa diakses, diukur ing "siji siji siji" uptime) lan **keandalan** (sistem berfungsi kanthi bener) iku krusial amarga panganggon kudu sistem sing bisa diakses lan berfungsi kanthi bener—lan paham bedane (sistem bisa ketersediaan tapi ora andal yen urip tapi apik hasil) murang prihatin sing padha tapi beda-beda.

Paham cara **raih ketersediaan dhuwur** iku pusatisasi: **redundansi** (macem-macem instance biso ora ana titik kegagalan tunggal—prinsip utama), sumebar ing zona/wilayah ketersediaan (idup nglawan kegagalan data center), **failover** (otomatis pindhah menyang backup), load balancing kanthi health checks, lan **ngilang titik kegagalan tunggal** ning mana-mana—iki iku teknik dhasar kanggo tetep urip sistem nglawan kegagalan.

Paham cara **bangun sistem sing andal**—**desain kanggo kegagalan** (anggep barang bakal gagal lan tangani kanthi apik, amarga kegagalan normal ing skala—mitane kunci), **toleransi kegagalan** (terus nglawan komponen gagal via retry, fallback, circuit breaker, lan graceful degradation), pengawasan, backup, lan ngindari kegagalan cascade—iki cermine resiliensi sing kudu kanggo produksi.

Ponten kunci yaiku ing skala, kegagalan ora biso dicegah, dadi sistem kudu dirancang kanggo tolerasi maneh (liwat redundansi lan toleransi kegagalan) tinimbang anggep kabeh becus.

Margane ketersediaan lan keandalan penting kanggo sistem produksi (panganggon butuh maneh urip lan berfungsi kanthi bener) lan raih maneh butuh redundansi, toleransi kegagalan, lan desain kanggo kegagalan, lan amarga paham konsep lan teknik iku penting kanggo desain sistem, paham ketersediaan lan keandalan iku kawruh dhasar lan penting sistem-desain—syarat non-fungsional kunci sing sistem produksi kudu cocok, kunci ing desain sistem resilient liwat redundansi lan toleransi kegagalan, lan cermine mitane desain-kanggo-kegagalan penting kanggo bangun sistem sing tetep urip lan berfungsi kanthi bener ing skala.