# MinIO Erasure Code Quickstart Guide [![Slack](https://slack.min.io/slack?type=svg)](https://slack.min.io)

MinIO protects data against hardware failures and silent data corruption using erasure code and checksums. With the highest level of redundancy, you may lose up to half (N/2) of the total drives and still be able to recover the data.

## What is Erasure Code?

// missing.  This is identified separately since this may need manual
// inspection to understand the root cause. E.g, this could be due to
// backend filesystem corruption.

// listOnlineDisks - returns
// - a slice of disks where disk having 'older' xl.meta (or nothing)
// are set to nil.
// - latest (in time) of the maximally occurring modTime(s), which has at least quorum occurrences.

        // Choice here is between failing with a correct RuntimeException
        // or mostly silently with an IOException
        url = urlLine.toHttpUrlOrNull() ?: throw IOException("Cache corruption for $urlLine").also {
          Platform.get().log("cache corruption", WARN, it)
        }
        requestMethod = source.readUtf8LineStrict()
        val varyHeadersBuilder = Headers.Builder()
        val varyRequestHeaderLineCount = readInt(source)

        if (!this.useNTSmbs) {
            log.debug("No support for NT SMBs");
        }

        // there seems to be a bug with some servers that causes corruption if using signatures +
        // CAP_LARGE_WRITE
        if (th.hasCapability(SmbConstants.CAP_LARGE_WRITEX) && !th.areSignaturesActive()) {

                        Math.min(th.getConfig().getReceiveBufferSize() - 70, th.areSignaturesActive() ? 0xFFFF - 70 : 0xFFFFFF - 70);
            }

            // there seems to be a bug with some servers that causes corruption if using signatures + CAP_LARGE_WRITE
            if (th.hasCapability(SmbConstants.CAP_LARGE_WRITEX) && !th.areSignaturesActive()) {
                this.writeSize = Math.min(th.getConfig().getSendBufferSize() - 70, 0xFFFF - 70);

    ([CVE-2020-15206](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15206))
*   Fixes a data corruption due to a bug in negative indexing support in TFLite,
    ([CVE-2020-15207](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15207))
*   Fixes a data corruption due to dimension mismatch in TFLite,
    ([CVE-2020-15208](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15208))

# See: https://github.com/bazelbuild/bazel/issues/5163
build:windows --features=compiler_param_file

# Use old toolchains for Windows builds.
build:windows --config=clang_local

# Do not risk cache corruption. See:
# https://github.com/bazelbuild/bazel/issues/3360
build:linux --experimental_guard_against_concurrent_changes

# Configure short or long logs
build:short_logs --output_filter=DONT_MATCH_ANYTHING

of internal (pointer, length) or (pointer, type) pairs,
as can be the case for interface values, maps,
slices, and strings in most Go implementations,
such races can in turn lead to arbitrary memory corruption.
</p>

<p>
Examples of incorrect synchronization are given in the
“Incorrect synchronization” section below.
</p>

<p>
Examples of the limitations on implementations are given in the

	}
	// Corrupt metadata, last 5 bytes is the checksum, so go a bit further back.
	trimmed[len(trimmed)-10] += 10
	if err := xl2.Load(trimmed); err == nil {
		t.Fatal("metadata corruption not detected")
	}
}

// TestUsesDataDir tests xlMetaV2.UsesDataDir
func TestUsesDataDir(t *testing.T) {
	vID := uuid.New()
	dataDir := uuid.New()
	transitioned := make(map[string][]byte)

the compiler that no Go pointers escape via the named C function.
If the noescape directive is used and the C function does not handle the
pointer safely, the program may crash or see memory corruption.

For example:

	// #cgo noescape cFunctionName

When a Go function calls a C function, it prepares for the C function to
call back to a Go function. The #cgo nocallback directive may be used to