Date: Tue, 05 Mar 2002 10:52:02 -0800 From: "Kevin Oberman" <oberman@es.net> To: Burhan Nazir <burhan@blueyonder.co.uk> Cc: Brett Glass <brett@lariat.org>, questions@freebsd.org Subject: Re: Softupdates on root in 4.5-RELEASE Message-ID: <20020305185203.F3F865D06@ptavv.es.net> In-Reply-To: Your message of "Tue, 05 Mar 2002 15:24:47 GMT." <20020305152447.GA25206@swansea.cableinet.net>
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> Date: Tue, 5 Mar 2002 15:24:47 +0000 > From: Burhan Nazir <burhan@blueyonder.co.uk> > Sender: owner-freebsd-questions@FreeBSD.ORG > > Softupdates will not write any data immediatly to the disk. I believe > it is about 30 seconds b4 any data actually gets wriiten. This enhances > disk write speed for certain types of operations. However, there is a > small risk of data loss/coruption if the machine looses power b4 any data was > written. For that reason, ppl believe that it is not a good idea to > have softupdates on the system critical root partition Ouch! I hope softupdates doesn't wait 30 seconds to write data to disk! What softupdates does do is order the writing of metadata so that it is, in theory, impossible to have corrupt metadata and thus eliminate the requirement for fsck before mounting as well as the possibility of a damaged disk structure. One of the side effects is that updating of the file system when files are deleted can be delayed for many seconds. Many systems only have 50 MB root systems and that is not a lot of slack. If you run softupdates on that partition and attempt a large number of updates (as with an installworld), new files will be written out without the free space on the disk being credited with the space taken by the old, replaced files. The result is an installation failure because the root file system is "full". If you enlarge your root system to 100 or 200 MB and keep root reasonably clean, this should not be a problem and softupdates can be turned on for the root system. One point of clarification...while a system running with softupdates does not REQUIRE an fsck to be safely returned to service, it does need one at some point to free up unused blocks that are still marked as in use. In V5.0 it is likely that background fsck will be implemented so that you boot back up and get the system functioning and then start fsck running in the background to get back deleted file space. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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