Date: Wed, 05 Mar 2014 08:17:28 -0600 From: Karl Denninger <karl@denninger.net> To: freebsd-fs@freebsd.org Subject: Re: Is LZ4 compression of the ZFS L2ARC available in any RELEASE/STABLE? Message-ID: <531731F8.1050000@denninger.net> In-Reply-To: <CAJ7kQyEp208XKt3CaiBufiB%2Bg_CHAkUgzAzVdX_6Gx2WyW1ENg@mail.gmail.com> References: <CAJ7kQyGTOuynOoLukXbP2E6GPKRiBWx8_mLEchk90WDKO%2Bo-SA@mail.gmail.com> <53157CC2.8080107@FreeBSD.org> <CAJ7kQyGQjf_WbY64bLVX=YfmJUfAd8i22kVbVhZhEWPMg7bbQw@mail.gmail.com> <5315D446.3040701@freebsd.org> <CAJ7kQyFf19Un_TS=kW=T21HT%2BoabhsUhJij5oixQ2_uh0LvHRA@mail.gmail.com> <alpine.GSO.2.01.1403042037290.1717@freddy.simplesystems.org> <CAJ7kQyEp208XKt3CaiBufiB%2Bg_CHAkUgzAzVdX_6Gx2WyW1ENg@mail.gmail.com>
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This is a cryptographically signed message in MIME format. --------------ms030307010802020605090308 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable It probably won't matter all that much. You need to profile this but you can get a decent idea what's going on from sysstat or iostat; look at the transaction count, size per transaction and percentage of time the disks are busy. I bet you find low transaction size, moderate count and very high disk busy percentages, which points to lots of head movement on an average basis compared against bytes moved. That's the paradigm where spinning rust loses, basically, and the only answers are to spread the I/O across more spindles so you get more positioner economy, go to faster-rotating drives with faster seek times or move to SSDs. If your I/O pattern is as I suspect the first thing to do is get the L2ARC off the rest of the pool's disks as that de-couples that I/O from the actual data storage. In mixed, small I/O environments this frequently will double total throughput and it costs you just one spindle, and it can be a small one too as the L2ARC requirement is modest. Making that L2ARC a SSD is an option but beware of using cheap ones there as fault-tolerance rules apply to L2ARC as they do to data disks (this is not true for a cache drive which is ignored if it posts errors and results in no data loss.) Presuming that doesn't provide enough boost the next logical move is to consider putting the DBMS on SSDs itself. That completely removes positioning latency and will result in a massive speed increase. On 3/5/2014 1:17 AM, Olav Gjerde wrote: > Currently I've set the recordsize to 8k, however I'm thinking maybe a > recordsize of 4k may more optimal? > This is because the compressratio with LZ4 is around 2.5 and this value= has > been constant for all my data while growing from a few megabytes to a > tenfold of gigabytes. > Maybe something I should play with to see if it makes a difference. > > > On Wed, Mar 5, 2014 at 3:40 AM, Bob Friesenhahn < > bfriesen@simple.dallas.tx.us> wrote: > >> On Tue, 4 Mar 2014, Olav Gjerde wrote: >> >> I managed to mess up who I replied to and Matthew replied back with a= good >>> answer which I think didn't reach the mailing list. >>> >>> I actually have a problem with query performance in one of my databas= es >>> related to running PostgreSQL on ZFS. Which is why I'm so interested = in >>> compression for the L2ARC Cache. The problem is random IO read were >>> creating a report were I aggregate 75000 rows takes 30 minutes!!! The= >>> table >>> that I query has 400 million rows though. >>> The dataset easily fit in memory, so if I run the same query again it= >>> takes >>> less than a second. >>> >> Make sure that your database is on a filesystem with zfs block-size >> matching the database block-size (rather than 128K). Otherwise far mo= re >> data may be read than needed, and likewise, writes may result in writi= ng >> far more data than needed. >> >> Regardless, L2ARC on SSD is a very good idea for this case. >> >> Bob >> -- >> Bob Friesenhahn >> bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfrie= sen/ >> GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ >> > > --=20 -- Karl karl@denninger.net --------------ms030307010802020605090308 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 KoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNDAzMDUxNDE3MjhaMCMGCSqGSIb3DQEJBDEW BBTY3trLA2blwIfyqsG+j6HVJKm0hTBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIG0BgkrBgEEAYI3EAQxgaYwgaMwgZ0xCzAJBgNV BAYTAlVTMRAwDgYDVQQIEwdGbG9yaWRhMRIwEAYDVQQHEwlOaWNldmlsbGUxGTAXBgNVBAoT EEN1ZGEgU3lzdGVtcyBMTEMxHDAaBgNVBAMTE0N1ZGEgU3lzdGVtcyBMTEMgQ0ExLzAtBgkq hkiG9w0BCQEWIGN1c3RvbWVyLXNlcnZpY2VAY3VkYXN5c3RlbXMubmV0AgEIMIG2BgsqhkiG 9w0BCRACCzGBpqCBozCBnTELMAkGA1UEBhMCVVMxEDAOBgNVBAgTB0Zsb3JpZGExEjAQBgNV BAcTCU5pY2V2aWxsZTEZMBcGA1UEChMQQ3VkYSBTeXN0ZW1zIExMQzEcMBoGA1UEAxMTQ3Vk YSBTeXN0ZW1zIExMQyBDQTEvMC0GCSqGSIb3DQEJARYgY3VzdG9tZXItc2VydmljZUBjdWRh c3lzdGVtcy5uZXQCAQgwDQYJKoZIhvcNAQEBBQAEggIAincT24V7zD6kZY4dVX92lV1OdyFl HfmwzLvVfF03hhQFnfnq5fjfSg/gu8TlUJS3xyspye692sa5VPtQ6xaVVgvkG0FvJD0kM7qe txsuFqrY1va/QYaioXxzpbTlX2D/6+2oAlZT2uL65NjI1TcwCI/tTpco9pxim++qbRS7Hvop asjwirEHMo0qWUz9I4Llz56L9ybuZ183Zm0b+bCgMfKVahGK9JjjWydNn/y984vmtIQsz7Bq 1GKZvxqzoiF+05NJcxXuCyv4Q77jExX+qMJJEN0luTZ/4uD+7BV9GDmkUMtnPftKSVD69Cra y/kQNOxEkQ1jwn2kS4/4ohWDc5zp7MlS3o8MEgJQTj1rKNm9ZV0059hb4l/PBwwOtgXo1cwk F5G9cA1hQVTTNLWMtDdWamRH7NYQY1APGW0minjBASQXTbd5wiL3bC+D6Nk6Of/UU8iRKvMN 9MRKq9ZTbRpR1Iwp2+sEw0daIsI5RR3Dj/OnOfN839zkeeCSecbxmL6N+fdiMVddrnM3E5Xe VAB4yOmzps6LykWvQpTC5iBSJelrVpEwx5aWNB+PHlSQhQ2lpkAlf+Bt02UESNW7Ww097uUP JqARXndP2CkWm9oEE6eUnbXzhE0EHCxrEyU+Puxia0llBrhqs2tohx/gyQ8E1StlxYpcC+Zs /Q3AHNsAAAAAAAA= --------------ms030307010802020605090308--
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