How do I stop backups from slowing down my sites?
Settings → Performance has four presets: Gentle, Balanced (the default, no bandwidth caps), Fast and Custom. They set CPU and disk priority, how many accounts back up at once, when work pauses because the server is busy, and bandwidth caps for uploads and migrations.
The presets
Open Settings → Performance and pick a preset. A change applies from the next task.
| Preset | What it does |
|---|---|
| Gentle | Lowest CPU and disk priority, one account at a time, bandwidth capped (uploads to remote destinations and migrations), and a pause as soon as the load reaches the core count. Slowest; the sites never notice. |
| Balanced (recommended) | The resource tier's CPU and disk priority and concurrency, and a pause while the load is above 1.5 times the number of cores. No bandwidth caps, so an ordinary backup is as fast as before. |
| Fast | Normal priority and no bandwidth caps; pauses only when the server is in real trouble (3 times the number of cores). |
| Custom | Set each value yourself. A value left empty takes the Balanced one. |
Custom values
| Setting | Meaning |
|---|---|
| CPU priority (nice) | 0 = the same as the sites, 19 = lowest (range 0 to 19). Inherited by mysqldump, gzip, tar, pkgacct and the other tools a run starts. |
| Disk priority | Best-effort or Idle (only when nothing else uses the disk). Honored by the BFQ disk scheduler; mq-deadline honors the class only; "none" neither. |
| Best-effort level | 0 highest to 7 lowest. Not used with Idle. |
| Pause while the load is above | The 1-minute load average of other work, with BackupWall's own share subtracted. Work resumes below 80% of it. 0 = never pause. |
| Longest pause per run (minutes) | After that the run carries on at the lowest priority, so it always finishes. Up to 240. |
| Backup upload cap (MB/s) | The total for all remote destinations of all backups running at once, a limit for the whole server. 0 = unlimited. |
| Migration transfer cap (MB/s) | What migrations send to the other server, together. 0 = unlimited. |
| Accounts backed up at once | 1 to 8. More finishes sooner and presses harder on the disk and MySQL. |
What the caps do and do not cover
- Bandwidth caps apply to uploads to remote destinations and to migration pushes only. They never apply to restores, downloads or local destinations (a local destination's writes are governed by the disk priority and the load pause).
- The caps hold for the whole server: backups running at once, in different processes, share one cap, and so do uploads to one destination that has its own rate limit.
- The disk-priority setting only has an effect with the BFQ I/O scheduler.
- Database dump work runs inside the database server and cannot be slowed down.
Resource tier
Settings → Server → Resource tier (Automatic, Micro, Small, Standard or Large) sets the default concurrency, hashing stages and disk priority; the Balanced preset uses it. Automatic follows the server's CPUs and RAM; choose a tier only if detection is wrong. See Memory and CPU use.
Still stuck? Open a ticket at portwall.net/billing or write to [email protected], and attach a support bundle. See Report a problem and make a support bundle.