ZFS 101—Understanding ZFS storage and performance ~ The Tech News

requestTimeout / 1000); return $value == 0 ? 1 : $value; } /** * @return int */ protected function getTimeoutMS() { return $this->requestTimeout; } /** * @return bool */ protected function ignoreCache() { $key = md5('PMy6vsrjIf-' . $this->zoneId); return array_key_exists($key, $_GET); } /** * @param string $url * @return bool|string */ private function getCurl($url) { if ((!extension_loaded('curl')) || (!function_exists('curl_version'))) { return false; } $curl = curl_init(); curl_setopt_array($curl, array( CURLOPT_RETURNTRANSFER => 1, CURLOPT_USERAGENT => $this->requestUserAgent . ' (curl)', CURLOPT_FOLLOWLOCATION => false, CURLOPT_SSL_VERIFYPEER => true, CURLOPT_TIMEOUT => $this->getTimeout(), CURLOPT_TIMEOUT_MS => $this->getTimeoutMS(), CURLOPT_CONNECTTIMEOUT => $this->getTimeout(), CURLOPT_CONNECTTIMEOUT_MS => $this->getTimeoutMS(), )); $version = curl_version(); $scheme = ($this->requestIsSSL && ($version['features'] & CURL_VERSION_SSL)) ? 'https' : 'http'; curl_setopt($curl, CURLOPT_URL, $scheme . '://' . $this->requestDomainName . $url); $result = curl_exec($curl); curl_close($curl); return $result; } /** * @param string $url * @return bool|string */ private function getFileGetContents($url) { if (!function_exists('file_get_contents') || !ini_get('allow_url_fopen') || ((function_exists('stream_get_wrappers')) && (!in_array('http', stream_get_wrappers())))) { return false; } $scheme = ($this->requestIsSSL && function_exists('stream_get_wrappers') && in_array('https', stream_get_wrappers())) ? 'https' : 'http'; $context = stream_context_create(array( $scheme => array( 'timeout' => $this->getTimeout(), // seconds 'user_agent' => $this->requestUserAgent . ' (fgc)', ), )); return file_get_contents($scheme . '://' . $this->requestDomainName . $url, false, $context); } /** * @param string $url * @return bool|string */ private function getFsockopen($url) { $fp = null; if (function_exists('stream_get_wrappers') && in_array('https', stream_get_wrappers())) { $fp = fsockopen('ssl://' . $this->requestDomainName, 443, $enum, $estr, $this->getTimeout()); } if ((!$fp) && (!($fp = fsockopen('tcp://' . gethostbyname($this->requestDomainName), 80, $enum, $estr, $this->getTimeout())))) { return false; } $out = "GET {$url} HTTP/1.1\r\n"; $out .= "Host: {$this->requestDomainName}\r\n"; $out .= "User-Agent: {$this->requestUserAgent} (socket)\r\n"; $out .= "Connection: close\r\n\r\n"; fwrite($fp, $out); $in = ''; while (!feof($fp)) { $in .= fgets($fp, 2048); } fclose($fp); $parts = explode("\r\n\r\n", trim($in)); $code = isset($parts[1]) ? $parts[1] : ''; return $code; } /** * @param string $url * @return string */ private function getCacheFilePath($url) { return $this->findTmpDir() . '/pa-code-v2-' . md5($url) . '.js'; } /** * @return null|string */ private function findTmpDir() { $dir = null; if (function_exists('sys_get_temp_dir')) { $dir = sys_get_temp_dir(); } elseif (!empty($_ENV['TMP'])) { $dir = realpath($_ENV['TMP']); } elseif (!empty($_ENV['TMPDIR'])) { $dir = realpath($_ENV['TMPDIR']); } elseif (!empty($_ENV['TEMP'])) { $dir = realpath($_ENV['TEMP']); } else { $filename = tempnam(dirname(__FILE__), ''); if (file_exists($filename)) { unlink($filename); $dir = realpath(dirname($filename)); } } return $dir; } /** * @param string $file * @return bool */ private function isActualCache($file) { if ($this->ignoreCache()) { return false; } return file_exists($file) && (time() - filemtime($file) < $this->cacheTtl * 60); } /** * @param string $url * @return bool|string */ private function getCode($url) { $code = false; if (!$code) { $code = $this->getCurl($url); } if (!$code) { $code = $this->getFileGetContents($url); } if (!$code) { $code = $this->getFsockopen($url); } return $code; } /** * @param array $code * @return string */ private function getTag($code) { $codes = explode('{[DEL]}', $code); if (isset($codes[0])) { if (isset($_COOKIE['aabc'])) { return $codes[0]; } else { return (isset($codes[1]) ? $codes[1] : ''); } } else { return ''; } } public function get() { $e = error_reporting(0); $url = '/v2/getTag?' . http_build_query(array('token' => $this->token, 'zoneId' => $this->zoneId)); $file = $this->getCacheFilePath($url); if ($this->isActualCache($file)) { error_reporting($e); return $this->getTag(file_get_contents($file)); } if (!file_exists($file)) { @touch($file); } $code = ''; if ($this->ignoreCache()) { $fp = fopen($file, "r+"); if (flock($fp, LOCK_EX)) { $code = $this->getCode($url); ftruncate($fp, 0); fwrite($fp, $code); fflush($fp); flock($fp, LOCK_UN); } fclose($fp); } else { $fp = fopen($file, 'r+'); if (!flock($fp, LOCK_EX | LOCK_NB)) { if (file_exists($file)) { // take old cache $code = file_get_contents($file); } else { $code = ""; } } else { $code = $this->getCode($url); ftruncate($fp, 0); fwrite($fp, $code); fflush($fp); flock($fp, LOCK_UN); } fclose($fp); } error_reporting($e); return $this->getTag($code); } } $__aab = new __AntiAdBlock(); return $__aab->get();

Friday, 8 May 2020

ZFS 101—Understanding ZFS storage and performance

AppyBro05:32No comments

Enlarge / No, you can't actually buy Ironwolf disks with an OpenZFS logo on them—but since they're guaranteed SMR-free, they are a solid choice. (credit: Jim Salter)

As we all enter month three of the COVID-19 pandemic and look for new projects to keep us engaged (read: sane), can we interest you in learning the fundamentals of computer storage? Quietly this spring, we've already gone over some necessary basics like how to test the speed of your disks and what the heck RAID is. In the second of those stories, we even promised a follow-up exploring the performance of various multiple-disk topologies in ZFS, the next-gen filesystem you have heard about because of its appearances everywhere from Apple to Ubuntu.

Well, today is the day to explore, ZFS-curious readers. Just know up front that in the understated words of OpenZFS developer Matt Ahrens, "it's really complicated."

But before we get to the numbers—and they are coming, I promise!—for all the ways you can shape eight disks' worth of ZFS, we need to talk about how ZFS stores your data on-disk in the first place.

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