Date: Sun, 21 Sep 2014 17:19:51 +0800 From: Xin Li <delphij@delphij.net> To: freebsd-scsi@freebsd.org Subject: Re: How to disable hard disk write cache? Message-ID: <541E9837.3060407@delphij.net> In-Reply-To: <541E91E4.4030802@gmx.de> References: <541804B0.7070407@gmail.com> <54184484.1070304@delphij.net> <541E8DAE.8010407@gmx.de> <541E8F72.4020202@delphij.net> <541E91E4.4030802@gmx.de>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 9/21/14 4:52 PM, Matthias Andree wrote: > Am 21.09.2014 um 10:42 schrieb Xin Li: >> On 9/21/14 4:34 PM, Matthias Andree wrote: >>> Am 16.09.2014 um 16:09 schrieb Xin Li: >> >>>> Modern SATA/SAS/SCSI devices usually comes with the >>>> capability of tagged commands, allowing the OS to know when a >>>> write buffer is on stable storage. With this, file systems >>>> can easily implement the right semantics and recover from >>>> e.g. a power outage, etc. >> >>> Yes, they *can easily implement* that, but which file systems >>> in FreeBSD *actually do* that? >> >> Both UFS (with Soft Updates, which is what it's all about; I >> haven't checked the Journalled Soft Updates case) and ZFS do that >> for ages. > > Thank you. Is this in any of the 9.3 manpages so I could look that > up rather than ask questions on the lists? :-) I don't really know... I personally see it as a vital feature for any file systems (or otherwise they become the cat who ate our homework :) so I doubt if it's actually being explicitly documented. This is probably a good FAQ candidate though. Cheers, -----BEGIN PGP SIGNATURE----- iQIbBAEBCgAGBQJUHpg3AAoJEJW2GBstM+nsQDoP+IFrhCT+1LEfDOQYcC29XRi3 SHwrkoMOXgnvw0/h0xTGxQ9pLDl9xLIwTmaWdFNtHM1hYUI1XzZC96GuNSEQfxuR G6VPIsj6mb/sE0+HphZmJHsM3QG2gC9aiFtMr6DggBa4bWokFpjWIigmKP4z5eFD 9a+q4P5tZFIJUoKeDHEyxDdaoxXRWcD7528ALF7MueJXj0Ej1ErPdr4yAi63YUar VrqGqPSRnyEf5h/wak5UGy4ETXZmIScAONYDjI7bwZaJbgO/3qn3AqiV+xVtPJol EVW8b3LjMuV0/d+aym02eVqb4CMPx8JE2Zb8cPl9oVBI386ej9NKzVQVrbL9SC+N Ogm4ScYQxYBI6k7fKg7L2Iy9K2zYHAIdBSRlFjVRipn8O8wt8yrTq0lZYxLpykIY g1+lVeguKZtntF1jg0r4Bnw0+qhJczXf/Xu7icnWIcOjzcAKd+cIXjHzb/0Jh1ZN RM7hEyR7aHW5nwwZPfpV+Q5KWCflc9XgUxxWVVgzXkWDhDMuCpTSGBi/ohjbgPs7 I0cj4IBH+S7fTLuRrkYyUaUg3Sqe3Z3A9Tkyr2q4ePq6RctigcDjVHfbFNpL10b0 PQfF2IqprcMdGoiqIZoQ82qpwSNizFKVzv7vLQnWvFd2Fr3Gh2XQbXWESDo33QfR VMxnrmQ8xrfBxX2Bn9g= =ZkPk -----END PGP SIGNATURE-----
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