Date: Fri, 29 Apr 2016 08:47:22 -0500 From: Karl Denninger <karl@denninger.net> To: freebsd-fs@freebsd.org Subject: Re: How to speed up slow zpool scrub? Message-ID: <08d59afe-c835-fa8d-0e52-78afcb1cc030@denninger.net> In-Reply-To: <alpine.GSO.2.20.1604290821210.23612@freddy.simplesystems.org> References: <381846248.2672053.1461695277122.JavaMail.yahoo.ref@mail.yahoo.com> <381846248.2672053.1461695277122.JavaMail.yahoo@mail.yahoo.com> <1461736217.1121.17.camel@michaeleichorn.com> <alpine.GSO.2.20.1604290821210.23612@freddy.simplesystems.org>
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This is a cryptographically signed message in MIME format. --------------ms070706040406030308010403 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 4/29/2016 08:31, Bob Friesenhahn wrote: > On Wed, 27 Apr 2016, Michael B. Eichorn wrote: >> >> It does not *need* to be ECC ram, ECC is just *highly recommended*. As= >> one of the key features of zfs is bitrot prevention, it makes sense to= >> protect against bitrot everywhere. Zfs (and thus freenas) is just fine= >> with non-ecc ram. Just, like for any filesystem if the bit is flipped >> in ram it will be recorded as such on disk. > > This is not necessarily the case. Zfs does not offer additional > protections for data in RAM. It assumes that data in RAM is protected > in other ways. The on-disk checksum only verifies that the data was > not modified since it was checksummed, but it may already be corrupt. > The risk factor is pretty high if RAM becomes corrupted since zfs uses > so much RAM. > > It is possible to lose data and even the whole pool due to memory > corruption. > > There are well known cases where users encountered continual/periodic > pool corruptions due to flaky RAM. > > Bob To amplify what Bob said using ZFS on a system without ECC RAM is just begging to lose the entire pool at some point due to a random bit-error in system memory and the fact that it happened may be completely concealed from you for quite a while until at a random later point in time you discover the pool is hopelessly corrupt. ZFS makes the *assumption*, fair or not, that everything in its RAM-based caches is correct. If that assumption is violated you will eventually be a very sad Panda. Use ECC memory or don't use ZFS. --=20 Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms070706040406030308010403 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Bl8wggZbMIIEQ6ADAgECAgEpMA0GCSqGSIb3DQEBCwUAMIGQMQswCQYDVQQGEwJVUzEQMA4G A1UECBMHRmxvcmlkYTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3Rl bXMgTExDMRwwGgYDVQQDExNDdWRhIFN5c3RlbXMgTExDIENBMSIwIAYJKoZIhvcNAQkBFhND dWRhIFN5c3RlbXMgTExDIENBMB4XDTE1MDQyMTAyMjE1OVoXDTIwMDQxOTAyMjE1OVowWjEL MAkGA1UEBhMCVVMxEDAOBgNVBAgTB0Zsb3JpZGExGTAXBgNVBAoTEEN1ZGEgU3lzdGVtcyBM TEMxHjAcBgNVBAMTFUthcmwgRGVubmluZ2VyIChPQ1NQKTCCAiIwDQYJKoZIhvcNAQEBBQAD ggIPADCCAgoCggIBALmEWPhAdphrWd4K5VTvE5pxL3blRQPyGF3ApjUjgtavqU1Y8pbI3Byg XDj2/Uz9Si8XVj/kNbKEjkRh5SsNvx3Fc0oQ1uVjyCq7zC/kctF7yLzQbvWnU4grAPZ3IuAp 3/fFxIVaXpxEdKmyZAVDhk9az+IgHH43rdJRIMzxJ5vqQMb+n2EjadVqiGPbtG9aZEImlq7f IYDTnKyToi23PAnkPwwT+q1IkI2DTvf2jzWrhLR5DTX0fUYC0nxlHWbjgpiapyJWtR7K2YQO aevQb/3vN9gSojT2h+cBem7QIj6U69rEYcEDvPyCMXEV9VcXdcmW42LSRsPvZcBHFkWAJqMZ Myiz4kumaP+s+cIDaXitR/szoqDKGSHM4CPAZV9Yh8asvxQL5uDxz5wvLPgS5yS8K/o7zDR5 vNkMCyfYQuR6PAJxVOk5Arqvj9lfP3JSVapwbr01CoWDBkpuJlKfpQIEeC/pcCBKknllbMYq yHBO2TipLyO5Ocd1nhN/nOsO+C+j31lQHfOMRZaPQykXVPWG5BbhWT7ttX4vy5hOW6yJgeT/ o3apynlp1cEavkQRS8uJHoQszF6KIrQMID/JfySWvVQ4ksnfzwB2lRomrdrwnQ4eG/HBS+0l eozwOJNDIBlAP+hLe8A5oWZgooIIK/SulUAsfI6Sgd8dTZTTYmlhAgMBAAGjgfQwgfEwNwYI KwYBBQUHAQEEKzApMCcGCCsGAQUFBzABhhtodHRwOi8vY3VkYXN5c3RlbXMubmV0Ojg4ODgw CQYDVR0TBAIwADARBglghkgBhvhCAQEEBAMCBaAwCwYDVR0PBAQDAgXgMCwGCWCGSAGG+EIB DQQfFh1PcGVuU1NMIEdlbmVyYXRlZCBDZXJ0aWZpY2F0ZTAdBgNVHQ4EFgQUxRyULenJaFwX RtT79aNmIB/u5VkwHwYDVR0jBBgwFoAUJHGbnYV9/N3dvbDKkpQDofrTbTUwHQYDVR0RBBYw FIESa2FybEBkZW5uaW5nZXIubmV0MA0GCSqGSIb3DQEBCwUAA4ICAQBPf3cYtmKowmGIYsm6 eBinJu7QVWvxi1vqnBz3KE+HapqoIZS8/PolB/hwiY0UAE1RsjBJ7yEjihVRwummSBvkoOyf G30uPn4yg4vbJkR9lTz8d21fPshWETa6DBh2jx2Qf13LZpr3Pj2fTtlu6xMYKzg7cSDgd2bO sJGH/rcvva9Spkx5Vfq0RyOrYph9boshRN3D4tbWgBAcX9POdXCVfJONDxhfBuPHsJ6vEmPb An+XL5Yl26XYFPiODQ+Qbk44Ot1kt9s7oS3dVUrh92Qv0G3J3DF+Vt6C15nED+f+bk4gScu+ JHT7RjEmfa18GT8DcT//D1zEke1Ymhb41JH+GyZchDRWtjxsS5OBFMzrju7d264zJUFtX7iJ 3xvpKN7VcZKNtB6dLShj3v/XDsQVQWXmR/1YKWZ93C3LpRs2Y5nYdn6gEOpL/WfQFThtfnat HNc7fNs5vjotaYpBl5H8+VCautKbGOs219uQbhGZLYTv6okuKcY8W+4EJEtK0xB08vqr9Jd0 FS9MGjQE++GWo+5eQxFt6nUENHbVYnsr6bYPQsZH0CRNycgTG9MwY/UIXOf4W034UpR82TBG 1LiMsYfb8ahQJhs3wdf1nzipIjRwoZKT1vGXh/cj3gwSr64GfenURBxaFZA5O1acOZUjPrRT n3ci4McYW/0WVVA3lDGCBRMwggUPAgEBMIGWMIGQMQswCQYDVQQGEwJVUzEQMA4GA1UECBMH RmxvcmlkYTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3RlbXMgTExD MRwwGgYDVQQDExNDdWRhIFN5c3RlbXMgTExDIENBMSIwIAYJKoZIhvcNAQkBFhNDdWRhIFN5 c3RlbXMgTExDIENBAgEpMA0GCWCGSAFlAwQCAwUAoIICTTAYBgkqhkiG9w0BCQMxCwYJKoZI hvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNjA0MjkxMzQ3MjJaME8GCSqGSIb3DQEJBDFCBEBk QPpKcj6iM6XPwVxyYGq73+Vn3pqio8qTo2c4pxTHz6wBwZxOkDwbeadmt4V8RogBKJisXdhR XIA2NPc3hwg/MGwGCSqGSIb3DQEJDzFfMF0wCwYJYIZIAWUDBAEqMAsGCWCGSAFlAwQBAjAK BggqhkiG9w0DBzAOBggqhkiG9w0DAgICAIAwDQYIKoZIhvcNAwICAUAwBwYFKw4DAgcwDQYI KoZIhvcNAwICASgwgacGCSsGAQQBgjcQBDGBmTCBljCBkDELMAkGA1UEBhMCVVMxEDAOBgNV BAgTB0Zsb3JpZGExEjAQBgNVBAcTCU5pY2V2aWxsZTEZMBcGA1UEChMQQ3VkYSBTeXN0ZW1z IExMQzEcMBoGA1UEAxMTQ3VkYSBTeXN0ZW1zIExMQyBDQTEiMCAGCSqGSIb3DQEJARYTQ3Vk YSBTeXN0ZW1zIExMQyBDQQIBKTCBqQYLKoZIhvcNAQkQAgsxgZmggZYwgZAxCzAJBgNVBAYT AlVTMRAwDgYDVQQIEwdGbG9yaWRhMRIwEAYDVQQHEwlOaWNldmlsbGUxGTAXBgNVBAoTEEN1 ZGEgU3lzdGVtcyBMTEMxHDAaBgNVBAMTE0N1ZGEgU3lzdGVtcyBMTEMgQ0ExIjAgBgkqhkiG 9w0BCQEWE0N1ZGEgU3lzdGVtcyBMTEMgQ0ECASkwDQYJKoZIhvcNAQEBBQAEggIAp7hEk/Z7 +Eo8f39yLrz2L2PINDsJTxgRh6xRxKQeUGPMqU4mh8+Fb5SfH0i2ZEZsS+91QeY88vCre/ZK 9HEdn0QWhskft3ejHnpcQg93VyH0DdM2vlxdOIDnRHsN9m7zqxmPyjOpVyPXl/BzZXfxtxBS YVf8JAyGwwuSRtv6u6MQYpCs/sf5shbqmgqyi3EgRfgdkAzpbVz2RPTa5vKazES0LWU18UnY O5i1jwmvBCTvnu648k74GImv6CtckIcYPt7BXSpvaps1t63uHzgRnvxSeHhfbwVIAdogjPVi z/SG0hKQhHe7uojvaR4im4E+qqmpIp8oGjy/DuinCZYa7+pTDhm7SWHenP6bm5dGBnioIiSd Z8Ndt1+1Y+vxZF7diw9n4+BwJzeMvBDcdq0B7jpcX8sOvjzd8yhB+8JGPEXDPxEbo/B/2495 08k7aDFcnxCst5TdruE+qHiGogCZfsThbngH1ItX/jQJwIEe3rMhiCbO2UsWaYs5zY0J6tZD 0E5hxommg+5YU9LLUPGLKFhOhYQNWh0CVPOGYhu9/AaRoo5cnl/A2No6GCSFtmfkdNlqoG+m gO5FS5wmPBy+oCxZbWiabivtULpFfK7/thOGDBl5E4m9RRvxK5WlB3DMhfucpQQicAOFWVV7 11fP8HYPjjuVNmPoxv7IHQ/jQ+IAAAAAAAA= --------------ms070706040406030308010403--
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