Date: Fri, 18 Sep 1998 12:49:26 -0700 From: brian@worldcontrol.com To: Robert Clark <Clark@open.org>, "freebsd-questions@FreeBSD.ORG" <freebsd-questions@FreeBSD.ORG> Subject: Re: Root Disk Backup. Message-ID: <19980918124926.A1848@top.worldcontrol.com> In-Reply-To: <36029DED.100E0A16@open.org>; from Robert Clark on Fri, Sep 18, 1998 at 10:52:45AM -0700 References: <36029DED.100E0A16@open.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 0, Robert Clark <Clark@open.org> wrote: > I'm trying to establish a set of tools that will minimize downtime when > a root disk fails. > Not because root disk failure is a frequent occurance, but when it > happens, its always a key system at a bad time. > Questions / assumptions: > FreeBSD can backup a HD even if their is no FS FreeBSD recognizes? (I've > worked with a few (non UNIX0 tools that need a (PC-style) partition > table to do their jobs.) > As long as the geometry of the replacement drive is the same, does this > approach sound feasible? yes. I do it all the time. > What commands / programs could I use under FreeBSD? cat /dev/rsd0 | gzip | > backupcopy > Is anyone else out there doing anything like this? Yes. > In order to keep the amount of time a station is down during root-disk > backups, I'm entertaining the idea of making the initial copy a disk to > disk process. (And dump the second disk to tape a few minutes later.) I > was hoping that disk to disk would be quite a bit faster than disk to > tape. Yes. Disk to Disk is far faster, and IMHO more reliable. > Compound Question: (More for info than for need.) > If you dump a binary image of said HD, compression won't do much. Even > if the HD is only 10% in use, the compression algorithm won't know what > is files, and what is deleted files. I generally get around 50% compression with gzip on the raw size of the disk. bzip2 is too slow because it doesn't like compressing large areas of similar data (blank sectors). A fully used filesystem might not have this problem. > Dumping a binary image of a "washed" disk would seem to be faster. I find copying a disk to disk runs at about a constant rate regardless of the data. The compression time can change. > Washed areas should be easier to compress. Yes gzip, No bzip2. -- Brian Litzinger <brian@litzinger.com> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19980918124926.A1848>