Date: Thu, 27 Mar 2014 09:53:41 -0500 From: Karl Denninger <karl@denninger.net> To: freebsd-fs@freebsd.org Subject: Re: zfs l2arc warmup Message-ID: <53343B75.6090807@denninger.net> In-Reply-To: <alpine.GSO.2.01.1403270904280.1735@freddy.simplesystems.org> References: <CAFfb-hpi20062%2BHCrSVhey1hVk9TAcOZAWgHSAP93RSov3sx4A@mail.gmail.com> <alpine.GSO.2.01.1403270904280.1735@freddy.simplesystems.org>
next in thread | previous in thread | raw e-mail | index | archive | help
This is a cryptographically signed message in MIME format. --------------ms070103020008010308040207 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable On 3/27/2014 9:26 AM, Bob Friesenhahn wrote: > On Thu, 27 Mar 2014, Joar Jegleim wrote: >> Is this how 'you' do it to warmup the l2arc, or am I missing something= ? >> >> The thing is with this particular pool is that it serves somewhere >> between 20 -> 30 million jpegs for a website. The front page of the >> site will for every reload present a mosaic of about 36 jpegs, and the= >> jpegs are completely randomly fetched from the pool. >> I don't know what jpegs will be fetched at any given time, so I'm >> installing about 2TB of l2arc ( the pool is about 1.6TB today) and I >> want the whole pool to be available from the l2arc . > > Your usage pattern is the opposite of what the ARC is supposed to do.=20 > The ARC is supposed to keep most-often accessed data in memory (or=20 > retired to L2ARC) based on access patterns. > > It does not seem necessary for your mosaic to be truely random across > 20 -> 30 million jpegs. Random across 1000 jpegs which are circulated > in time would produce a similar effect. > > The application building your web page mosiac can manage which files=20 > will be included in the mosaic and achieve the same effect as a huge=20 > cache by always building the mosiac from a known subset of files. The=20 > 1000 jpegs used for the mosaics can be cycled over time from a random=20 > selection, with old ones being removed. This approach assures that=20 > in-memory caching is effective since the same files will be requested=20 > many times by many clients. > > Changing the problem from an OS-oriented one to an=20 > application-oriented one (better algorithm) gives you more control and = > better efficiency. > > Bob That's true, but the other option if he really does want it to be random = across the entire thing, given the size (which is not outrageous) and=20 that the resource is going to be read-nearly-only, is to put them on=20 SSDs and ignore the L2ARC entirely. These days that's not a terribly=20 expensive answer as with a read-mostly-always environment you're not=20 going to run into a rewrite life-cycle problem on rationally-priced SSDs = (e.g. Intel 3500s). Now an ARC cache miss is not all *that* material since there is no seek=20 or rotational latency penalty. HOWEVER, with that said it's still expensive compared against rotating=20 rust for bulk storage, and as Bob noted a pre-select middleware process=20 would result in no need for a L2ARC and allow the use of a pool with=20 much-smaller SSDs for the actual online retrieval function. Whether the coding time and expense is a good trade against the lower=20 hardware cost to do it the "raw" way is a fair question. --=20 -- Karl karl@denninger.net --------------ms070103020008010308040207 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIFTzCC BUswggQzoAMCAQICAQgwDQYJKoZIhvcNAQEFBQAwgZ0xCzAJBgNVBAYTAlVTMRAwDgYDVQQI EwdGbG9yaWRhMRIwEAYDVQQHEwlOaWNldmlsbGUxGTAXBgNVBAoTEEN1ZGEgU3lzdGVtcyBM TEMxHDAaBgNVBAMTE0N1ZGEgU3lzdGVtcyBMTEMgQ0ExLzAtBgkqhkiG9w0BCQEWIGN1c3Rv bWVyLXNlcnZpY2VAY3VkYXN5c3RlbXMubmV0MB4XDTEzMDgyNDE5MDM0NFoXDTE4MDgyMzE5 MDM0NFowWzELMAkGA1UEBhMCVVMxEDAOBgNVBAgTB0Zsb3JpZGExFzAVBgNVBAMTDkthcmwg RGVubmluZ2VyMSEwHwYJKoZIhvcNAQkBFhJrYXJsQGRlbm5pbmdlci5uZXQwggIiMA0GCSqG SIb3DQEBAQUAA4ICDwAwggIKAoICAQC5n2KBrBmG22nVntVdvgKCB9UcnapNThrW1L+dq6th d9l4mj+qYMUpJ+8I0rTbY1dn21IXQBoBQmy8t1doKwmTdQ59F0FwZEPt/fGbRgBKVt3Quf6W 6n7kRk9MG6gdD7V9vPpFV41e+5MWYtqGWY3ScDP8SyYLjL/Xgr+5KFKkDfuubK8DeNqdLniV jHo/vqmIgO+6NgzPGPgmbutzFQXlxUqjiNAAKzF2+Tkddi+WKABrcc/EqnBb0X8GdqcIamO5 SyVmuM+7Zdns7D9pcV16zMMQ8LfNFQCDvbCuuQKMDg2F22x5ekYXpwjqTyfjcHBkWC8vFNoY 5aFMdyiN/Kkz0/kduP2ekYOgkRqcShfLEcG9SQ4LQZgqjMpTjSOGzBr3tOvVn5LkSJSHW2Z8 Q0dxSkvFG2/lsOWFbwQeeZSaBi5vRZCYCOf5tRd1+E93FyQfpt4vsrXshIAk7IK7f0qXvxP4 GDli5PKIEubD2Bn+gp3vB/DkfKySh5NBHVB+OPCoXRUWBkQxme65wBO02OZZt0k8Iq0i4Rci WV6z+lQHqDKtaVGgMsHn6PoeYhjf5Al5SP+U3imTjF2aCca1iDB5JOccX04MNljvifXgcbJN nkMgrzmm1ZgJ1PLur/ADWPlnz45quOhHg1TfUCLfI/DzgG7Z6u+oy4siQuFr9QT0MQIDAQAB o4HWMIHTMAkGA1UdEwQCMAAwEQYJYIZIAYb4QgEBBAQDAgWgMAsGA1UdDwQEAwIF4DAsBglg hkgBhvhCAQ0EHxYdT3BlblNTTCBHZW5lcmF0ZWQgQ2VydGlmaWNhdGUwHQYDVR0OBBYEFHw4 +LnuALyLA5Cgy7T5ZAX1WzKPMB8GA1UdIwQYMBaAFF3U3hpBZq40HB5VM7B44/gmXiI0MDgG CWCGSAGG+EIBAwQrFilodHRwczovL2N1ZGFzeXN0ZW1zLm5ldDoxMTQ0My9yZXZva2VkLmNy bDANBgkqhkiG9w0BAQUFAAOCAQEAZ0L4tQbBd0hd4wuw/YVqEBDDXJ54q2AoqQAmsOlnoxLO 31ehM/LvrTIP4yK2u1VmXtUumQ4Ao15JFM+xmwqtEGsh70RRrfVBAGd7KOZ3GB39FP2TgN/c L5fJKVxOqvEnW6cL9QtvUlcM3hXg8kDv60OB+LIcSE/P3/s+0tEpWPjxm3LHVE7JmPbZIcJ1 YMoZvHh0NSjY5D0HZlwtbDO7pDz9sZf1QEOgjH828fhtborkaHaUI46pmrMjiBnY6ujXMcWD pxtikki0zY22nrxfTs5xDWGxyrc/cmucjxClJF6+OYVUSaZhiiHfa9Pr+41okLgsRB0AmNwE f6ItY3TI8DGCBQowggUGAgEBMIGjMIGdMQswCQYDVQQGEwJVUzEQMA4GA1UECBMHRmxvcmlk YTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3RlbXMgTExDMRwwGgYD VQQDExNDdWRhIFN5c3RlbXMgTExDIENBMS8wLQYJKoZIhvcNAQkBFiBjdXN0b21lci1zZXJ2 aWNlQGN1ZGFzeXN0ZW1zLm5ldAIBCDAJBgUrDgMCGgUAoIICOzAYBgkqhkiG9w0BCQMxCwYJ KoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNDAzMjcxNDUzNDFaMCMGCSqGSIb3DQEJBDEW BBQ7vQUw9e9T8sirDYLM+T2VhuHmVDBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIG0BgkrBgEEAYI3EAQxgaYwgaMwgZ0xCzAJBgNV BAYTAlVTMRAwDgYDVQQIEwdGbG9yaWRhMRIwEAYDVQQHEwlOaWNldmlsbGUxGTAXBgNVBAoT EEN1ZGEgU3lzdGVtcyBMTEMxHDAaBgNVBAMTE0N1ZGEgU3lzdGVtcyBMTEMgQ0ExLzAtBgkq hkiG9w0BCQEWIGN1c3RvbWVyLXNlcnZpY2VAY3VkYXN5c3RlbXMubmV0AgEIMIG2BgsqhkiG 9w0BCRACCzGBpqCBozCBnTELMAkGA1UEBhMCVVMxEDAOBgNVBAgTB0Zsb3JpZGExEjAQBgNV BAcTCU5pY2V2aWxsZTEZMBcGA1UEChMQQ3VkYSBTeXN0ZW1zIExMQzEcMBoGA1UEAxMTQ3Vk YSBTeXN0ZW1zIExMQyBDQTEvMC0GCSqGSIb3DQEJARYgY3VzdG9tZXItc2VydmljZUBjdWRh c3lzdGVtcy5uZXQCAQgwDQYJKoZIhvcNAQEBBQAEggIAiShagBFjtv4mJfr5dM6KaCphMWk1 TPVGgOfjSJsuB2umaQ9aKtQt+KHnLkzasM113siATi9qvwJwG1foiCyHx+kBmZO3xk5Uciz8 TogYln/c/Xa+EfHb9y2dQw5ODXAugv813wIBp3I9fhrSaQJY5mCROaxi5BEu8+8Bk7dMS8fK BbKlPg4KpWWmszF74n5EI2+IJrWsiSUw3esNzwEavlsavRhwsimkAPjvBZhksNUTpRp/inFs NezYZRwTtSNflY+XCyMszqj1H2PwcpXvammzg0/nQ8Lz6Jrq5xzIbL7pfgBEhoocRQ/P4i9z itbK14a+PxVOIU6lUKiIRUCyOVtBLUkbv0U4w2nR/dMpxXWkjNFcdrKKvYW7t6B2JbPYYAXx I2zRZZZFFsed0segtnio73A67yt7PMpFER+wZkJX5XbhOa0OV9EhJ4kg1oNI4gs8UF3yGhrm ULnvfya7QIsdICp/CaNViP/KPcrlqPiWBhpiIpD5zut9O13ABh+ocP/YgYXhc11MJOyPtpXY T2DEJ4hWazMOTcBw6P6RLgnFkNLheJnrXwOeSl8jhc7sb4ybIfvjUeyaLy3YFSnl0OftP82c siAjT5x/Aa0VG38d3qqPo3jSow7FRR34KeNwLhja7uCYpgnoww3LuF1NqFxK784mbh9MqA3m yZBzuR4AAAAAAAA= --------------ms070103020008010308040207--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?53343B75.6090807>