From owner-freebsd-hackers Thu May 6 13: 3:40 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from smtp.enteract.com (thor.enteract.com [207.229.143.11]) by hub.freebsd.org (Postfix) with SMTP id 7946615A5D for ; Thu, 6 May 1999 13:02:42 -0700 (PDT) (envelope-from dscheidt@enteract.com) Received: (qmail 4791 invoked from network); 6 May 1999 20:02:41 -0000 Received: from shell-1.enteract.com (dscheidt@207.229.143.40) by thor.enteract.com with SMTP; 6 May 1999 20:02:41 -0000 Received: from localhost (dscheidt@localhost) by shell-1.enteract.com (8.9.3/8.9.2) with SMTP id PAA47276; Thu, 6 May 1999 15:02:38 -0500 (CDT) (envelope-from dscheidt@enteract.com) X-Authentication-Warning: shell-1.enteract.com: dscheidt owned process doing -bs Date: Thu, 6 May 1999 15:02:38 -0500 (CDT) From: David Scheidt To: Zhihui Zhang Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Copies of superblocks in FFS In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Thu, 6 May 1999, Zhihui Zhang wrote: :If the primary superblock (the second copy in cylinder group 0, at offset :8192+8192) is updated and other superblocks are not updated at the same :time, how can any of other copies be used to restore file system in case :that the primary copy is corrupted somehow? If so, the performance will :be degraded. Most of what is in the superblock is static, and doesn't change from filesystem creation time. The things that don't can be created from the disk, at fsck time. fsck -b has saved a lot of filesystems, and is clearly worth a few wasted blocks. : :Also, except for the root filesystem (/), all other filesystems (/var, :/usr, etc.) do not have the (boot code + disklabel) installed, these space :are also wasted (8192 bytes for each non-root filesystem). It is very handy to be able to make a filesytem bootable after it has been created. Much easier than dumping the filesytem, remaking the filesytem, and then restoring it. I'll pay 16K per filesystem for this. : :BTW, the hard disks are more stable nowadays and any bad sectors may have :been hidden by the disk controllers (the filesystem does not have to deal :with them). Panics still can leave the primary superblock hosed. Trust me. David Scheidt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message