# Erasure code sizing guide

## Toy Setups

Capacity constrained environments, MinIO will work but not recommended for production.

| servers | drives (per node) | stripe_size | parity chosen (default) | tolerance for reads (servers) | tolerance for writes (servers) |
|--------:|------------------:|------------:|------------------------:|------------------------------:|-------------------------------:|

A stand-alone MinIO server would go down if the server hosting the drives goes offline. In contrast, a distributed MinIO setup with _m_ servers and _n_ drives will have your data safe as long as _m/2_ servers or _m*n_/2 or more drives are online.

For example, an 16-server distributed setup with 200 drives per node would continue serving files, up to 4 servers can be offline in default configuration i.e around 800 drives down MinIO would continue to read and write objects.

package cmd

import (
	"os"
	"syscall"
)

var (
	// Disallow updating access times
	// Add non-block to avoid syscall to attempt to set epoll on files.
	readMode = os.O_RDONLY | 0x40000 | syscall.O_NONBLOCK // O_NOATIME

	// Write with data sync only used only for `xl.meta` writes
	writeMode = 0x1000 | syscall.O_NONBLOCK // O_DSYNC

	ch := make(chan madmin.SpeedTestResult, 1)
	go func() {
		defer xioutil.SafeClose(ch)

		concurrency := opts.concurrencyStart

		if opts.autotune {
			// if we have less drives than concurrency then choose
			// only the concurrency to be number of drives to start
			// with - since default '32' might be big and may not
			// complete in total time of 10s.
			if globalEndpoints.NEndpoints() < concurrency {

describes everything that can be configured in a MinIO setup, such as '--address', '--console-address' and command line arguments for the MinIO server.

Historically everything to MinIO was provided via command arguments for the hostnames and the drives via an ellipses syntax such as `minio server http://host{1...4}/disk{1...4}` this requirement added an additional burden to have sequential hostnames for us to make sure that we can provide horizontal distribution, however we have come across situations...

	driveOfflineCountMD = NewGaugeMD(driveOfflineCount,
		"Count of offline drives")
	driveOnlineCountMD = NewGaugeMD(driveOnlineCount,
		"Count of online drives")
	driveCountMD = NewGaugeMD(driveCount,
		"Count of all drives")

	// iostat related
	driveReadsPerSecMD = NewGaugeMD(driveReadsPerSec,
		"Reads per second on a drive",
		allDriveLabels...)

func CallerFrame() runtime.Frame {
	pcs := [13]uintptr{}
	// the third caller usually from gorm internal
	len := runtime.Callers(3, pcs[:])
	frames := runtime.CallersFrames(pcs[:len])
	for i := 0; i < len; i++ {
		// second return value is "more", not "ok"
		frame, _ := frames.Next()
		if (!strings.HasPrefix(frame.File, gormSourceDir) ||
			strings.HasSuffix(frame.File, "_test.go")) && !strings.HasSuffix(frame.File, ".gen.go") {

	n, err = c.Conn.Read(b)
	return n, err
}

// Write - writes data to the connection.
func (c *DeadlineConn) Write(b []byte) (n int, err error) {
	if c.abortWrites.Load() {
		return 0, context.DeadlineExceeded
	}
	c.setWriteDeadline()
	n, err = c.Conn.Write(b)
	return n, err
}

// SetDeadline will set the deadline for reads and writes.
// A zero value for t means I/O operations will not time out.

// errRPCAPIVersionUnsupported - unsupported rpc API version.
var errRPCAPIVersionUnsupported = errors.New("Unsupported rpc API version")

// errServerTimeMismatch - server times are too far apart.
var errServerTimeMismatch = errors.New("Server times are too far apart")

// errInvalidRange - returned when given range value is not valid.
var errInvalidRange = errors.New("Invalid range")

	return nil, fmt.Errorf("%w (offline-disks=%d/%d)", errErasureReadQuorum, disksNotFound, len(p.readers))
}

// Decode reads from readers, reconstructs data if needed and writes the data to the writer.
// A set of preferred drives can be supplied. In that case they will be used and the data reconstructed.