Date: Thu, 23 Mar 1995 06:54:43 -0500 (EST) From: william pechter ILEX <pechter@stars.sed.monmouth.army.mil> To: bde@zeta.org.au (Bruce Evans) Cc: FreeBSD-hackers@wcarchive.cdrom.com (FreeBSD-hackers) Subject: Re: Why IDE is bad Message-ID: <199503231155.DAA13542@wcarchive.cdrom.com> In-Reply-To: <199503231045.UAA11233@godzilla.zeta.org.au> from "Bruce Evans" at Mar 23, 95 08:45:18 pm
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> >Yeah, we all know that but ext2fs is doing it for ages now and they > >don't have that much more problem with it... It would be great if > >it worked (for the news spool for example). > > Why don't they have much of a problem with it? I can think of the following > possible reasons: > > 1) with more disk updates, there is more likely to be a failure in the > middle of an update. > a) If the failure is in software and unrelated to the file system > (e.g., a panic for a NULL pointer), then synchronous update > guarantees that the file system (but not the data) can be fixed up > by fsck, but fsck will find problems more often and more data will > be lost. More apparent-problems are bad publicity and lost data > is always annoying. > b) If the failure is in hardware, then synchronous update > doesn't guarantee anything. Metadata may be half written and > you'll be lucky if fsck can't read the bad half. The higher > reliablity of modern drives reduces the disadvantage of > synchronous update here. > c) If the failure is in software and is related to the file system, > then synchronous update doesn't guarantee anything. Metadata > may be scrambled and fsck will normally be able to read it and > become confused :-]. > 2) ext2fs may be more robust. It's never assumed synchronous updates. > 3) ext2fsck may be better than fsck. > 4) writing the disk more may wear it out faster. > > Bruce > One question is -- should we just port ext2fs? (There's already a lot of people experimenting with both FreeBSD and Linux. There's already a read-only port of FFS to Linux. One drawback is the need to make ALL the BSD utilities (dump, restore, etc.) play nice with ext2fs. (One reason I went to BSD from Linux was the lack of dump/restore). Cpio and tar do not make a backup scheme. Bill ----------------------------------------------------------------------------- Bill Pechter |Systems Administrator | Ilex Systems |170 Patterson Ave | Shrewsbury, New Jersey 07702 908-532-2369 |pechter@sesd.ilex.com | pechter@stars.sed.monmouth.army.mil
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