Date: Thu, 26 Mar 2015 23:44:17 -0400 From: Allan Jude <allanjude@freebsd.org> To: freebsd-hackers@freebsd.org Subject: Re: Seagate Archive HDD Message-ID: <5514D211.406@freebsd.org> In-Reply-To: <5514D0A9.1040106@delphij.net> References: <alpine.BSF.2.20.1503261124380.1417@laptop.wojtek.intra> <55148E42.80708@delphij.net> <4F65B315-5FFE-4184-91FD-C05A40E0A26E@dons.net.au> <5514A133.8060409@delphij.net> <88DE4F68-B05E-4E4D-8C4A-DED8147172E7@dons.net.au> <CAJ-VmokEQjDXSHTn7o%2BEDnyrjDxckQkvWgQokKhhY1T1m3t_wA@mail.gmail.com> <5514D0A9.1040106@delphij.net>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --6Ghx9WbxclRj4PV7eBU6xaLLiXXSc1PId Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 2015-03-26 23:38, Xin Li wrote: >=20 >=20 > On 3/26/15 17:58, Adrian Chadd wrote: >> ... all the talk about this stuff, and yet noone's talked about >> how ZFS is supposed to be append only, and boy wouldn't that be >> awesome. :) >=20 > It doesn't overwrite existing data with the assumption that a, let's > say, 4K-native drive doesn't have a 1MB "band" when writing. >=20 > I hope the "journal" would be helpful for this assuming it is on > non-volatile medium... >=20 > Cheers, > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.o= rg" >=20 Also, ZFS does write to the vdev label (256kb each, 2x at the front and 2x at the end of the drive) frequently (every transaction group, so at a minimum, every 5 seconds by default). The vdev label has a ring of uberblocks, that then point to the most recent metadata. If there was some special place on disk these could be located to avoid being part of a large band, and avoid the write amplification, that would likely make a big difference. --=20 Allan Jude --6Ghx9WbxclRj4PV7eBU6xaLLiXXSc1PId Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (MingW32) iQIcBAEBAgAGBQJVFNIVAAoJEJrBFpNRJZKfPDcP/i8h1Iu4vJO7JQ4orZ7TIspj BuzVZIfJlufQwRbYNIEy1ttaHsiQG9ISqwgL/9uyG39UpWvCvXnMlWiWtwiF8Psn ++y04DPgoaY68NsPpsslhiHqCBlV5sHdUrfBlRHSAABqOtPWbsjQH/u1xOaMhD9T 4nFtZFwvdikMS20P823W0sBa42uKBceg+wRaBlRnvuxes6GCTABmsCgjhDk7Xtii LVZg3wMh2kWScOGlHFzsQ8PsZfYaFdMnRQsyuowD3a5dkCyDt3ixDJwUjzYQ4B9N Kr8EzuvxKNkVRyF/+f9JpM1AxJKXl8SitdczTEhLFsFwIsihBW9PZ+MEcTwiO3e0 XnTCW/NsTnW7Vx9eaKtQaYN9p8RPlShrLbcwpoCmAZLc7T0RqZTXJojvt+6pVcz+ +MwTZpixgxIDTXCG2a45fOKriUiCE/4Hp034A4k8kIJ27qiThgCG4413wpOvd/hJ TsVOgHijAQHbVQWFzvSuPBbaSuFEBWyPskwxpZxaalQ14UkTClosattHpvMEae0L ap4V6AYo4PX269eoQjxOA1ASlpwM2ch5oBFiCE+7e5ejoNY1jdGDMl2eVmCyTJmf j432qTn5J+ciXX+IONIgCg5wY5cqd3RaA+qMFIb7tPQ49zrEyV3oa+MiDXIfKE2R EnozFMLCwV8lVzzoFOy/ =8p9X -----END PGP SIGNATURE----- --6Ghx9WbxclRj4PV7eBU6xaLLiXXSc1PId--
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