Volume resizing for running sandboxes - Documentation

You can resize a volume while its sandbox is running. The operation typically completes in under one second.

Limitations

You can increase a volume’s size but cannot decrease it
Blaxel does not currently provide built-in automatic resizing

Resizing strategy

To avoid running out of disk space:

Check volume usage before file-intensive commands such as package installations
Resize the volume when usage approaches 80%
Run a periodic monitor in the sandbox to measure usage and trigger resizing

Monitor and resize a volume

The following function checks disk usage every three seconds and doubles the volume size when usage reaches 80%:

import { SandboxInstance, VolumeInstance } from "@blaxel/core";

async function startVolumeMonitor(
  sandbox: SandboxInstance,
  volumeName: string,
  mountPath: string,
  initialSizeMB: number,
  usageThresholdPercent: number = 80,
  growthFactor: number = 2,
  pollIntervalSeconds: number = 3,
) {
  let currentSizeMB = initialSizeMB;
  let resizing = false;

  const monitorCmd = `while true; do df -m ${mountPath}; sleep ${pollIntervalSeconds}; done`;

  await sandbox.process.exec({
    command: monitorCmd,
    onLog: (log) => {
      const lines = log.split("\n");

      for (const line of lines) {
        if (!line.includes(mountPath) || line.startsWith("Filesystem")) continue;

        const parts = line.trim().split(/\s+/);
        if (parts.length < 5) continue;

        const usagePercent = parseInt(parts[4]!.replace("%", ""), 10);
        if (isNaN(usagePercent)) continue;

        console.log(
          `[monitor] ${parts[2]}MB used / ${parts[1]}MB total (${usagePercent}%)`,
        );

        if (usagePercent >= usageThresholdPercent && !resizing) {
          resizing = true;
          const newSize = Math.ceil(currentSizeMB * growthFactor);

          console.log(
            `[monitor] Usage ${usagePercent}% >= ${usageThresholdPercent}%, resizing ${currentSizeMB}MB to ${newSize}MB`,
          );

          VolumeInstance.update(volumeName, { size: newSize })
            .then(() => {
              currentSizeMB = newSize;
              console.log(`[monitor] Resize to ${newSize}MB complete`);
            })
            .catch((err) => {
              console.error("[monitor] Resize failed:", err);
            })
            .finally(() => {
              resizing = false;
            });
        }
      }
    },
  });

  return {
    getCurrentSize: () => currentSizeMB,
  };
}

Adjust the threshold, growth factor, and polling interval for your workload.

Volumes overview

Create, inspect, resize, and delete volumes.

Volumes for sandboxes

Attach persistent storage to a sandbox.

Last modified on October 5, 2026