From owner-freebsd-questions Fri Nov 15 6:29:29 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9953C37B401 for ; Fri, 15 Nov 2002 06:29:26 -0800 (PST) Received: from sage-one.net (adsl-65-71-135-137.dsl.crchtx.swbell.net [65.71.135.137]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1ED1243E6E for ; Fri, 15 Nov 2002 06:29:25 -0800 (PST) (envelope-from jackstone@sage-one.net) Received: from sagea (sagea [192.168.0.3]) by sage-one.net (8.11.6/8.11.6) with SMTP id gAFETAD49755; Fri, 15 Nov 2002 08:29:12 -0600 (CST) (envelope-from jackstone@sage-one.net) Message-Id: <3.0.5.32.20021115082905.010abd98@mail.sage-one.net> X-Sender: jackstone@mail.sage-one.net X-Mailer: QUALCOMM Windows Eudora Pro Version 3.0.5 (32) Date: Fri, 15 Nov 2002 08:29:05 -0600 To: Mark , From: "Jack L. Stone" Subject: Re: restore question In-Reply-To: <200211150425.GAF4PFI21317@asarian-host.net> References: <020901c28b6f$f0b241c0$1200a8c0@gsicomp.on.ca> <127.0.0.1.20021114195745.01099888@mail.sage-one.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG At 05:25 AM 11.15.2002 +0100, Mark wrote: >----- Original Message ----- >From: "Jack L. Stone" >To: "Mark" ; "Matthew Emmerton" >; "R. Zoontjens" ; > >Sent: Friday, November 15, 2002 2:57 AM >Subject: Re: restore question > > > >> There IS a program similar to Ghost with respect to making an image. >> It's called "dd" and it's already installed on your FBSD system. >> Run "man 1 dd" for options. >> >> Bear in mind that if you want an image of your whole disk, you'll need >> the 2nd one to be at least equal in size, but you will lose any part of >the >> 2nd HD that is larger than HD #1 (I think Ghost does that too >> -- or used to). dd can be limited to imaging only a slice however..... >> >> This questions comes up monthly and the archives has numerous postings >> over the past several months that will fill more details..... > > >Yes, the question comes up many times; yet the right answer keeps lacking. >:) Before I asked, I had, of course, done a bit of searching. And found that >there are many disadvantages to using "dd". > >For one, using disk-blocks, instead of reading files sequentially, like tar >and Ghost do, enhances the risk of data-corruption. > >For two, with "dd" you need to unmount filesystems first. Which makes it >pretty useless on a production server. Yeah, like I can really afford to >have my /usr slice be absent for half-an-hour. I think not. :) > >Actually, we are talking about backup, but the real issue is restore. >Everybody can make a tar of the root system, or a dd image. Sure. Restoring >it, however, in a manner that will yield you a bootable, instant runnable >system, now that is another matter. And what to do with special cases like >/dev? > >In all my perusing the net, I have yet to encounter one solution that said: >"This is how you can make a full system backup, with this image, that you >can immediately restore on a blank harddisk, and have your system up and >running again." > >Many suggestions I read about ways to backup. But, like I said, restoring is >the real issue. I can backup /proc for sure; the wisdom of restoring it on a >life system, however, is another matter. That is why the only clean way of >doing this, would be to make a disk-image, like Ghost does. And Ghost, so >unlike dd, does NOT use disk-blocks, but reads files sequentially. When >making a disk image, Ghost basically just does several partition images, and >then adds partition table info to the overall disk image. No need to "zero" >out the disk first, like with dd, so as not to have it waste too much space. > >Still looking... > >- Mark > Your research is a little short of the mark. I have made bootable backups many times using dd and dump/restore -- yes, and on a "live system" too. With a 40GB HD with 1GH CPU, a dd can be done in about 15 mins. That speed depends too on the "bs=xxx" size used all the way from 1024 to 1m. You can check the I/O speed like this: Here's an example with an IDE drive: #iostat ad0 1 tty ad0 cpu tin tout KB/t tps MB/s us ni sy in id 0 3 5.19 7 0.03 11 0 4 1 84 0 126 127.36 183 22.74 0 0 6 2 92 0 44 128.00 190 23.76 0 0 2 0 98 0 44 128.00 191 23.89 0 0 5 0 95 0 44 128.00 191 23.88 0 0 7 1 92 As you can see, it's really doing 128 kB transfers, for an average transfer rate of almost 24 MB/s. I've used 8192 and found it wasn't necessary to even run fsck on the backed-up HD... just switched the cables and booted right up. You will probably have to run fsck on dd'd HD images. I prefer to use a dump/restore script (tabkes care of FDISK/LABEL too) that keeps a bootable backup hard disk always at the ready (I also move backups across the network for more safety and have restored that on another HD with 100% success). Also, should I want to switch HDs around, I just run the script before shutdown. I've done it many times on a live system, but dropping down to single user is recommended. With dump/restore, I can backup a HD with 6GB in less than 10 mins. Yes, it is a busy box that I can't afford to have down any longer than necessary. I don't know what more you could want... there is NO Ghost that will work to my knowledge. I've done all of the same long searching just like you, but dump/restore is one of the SAFEST way of moving file systems..... The handbook says it IS the safeest way. If you want to do it right, study up on dump/restore. I don't trust tar for live filesystems, or to keep permission/links straight although many do use tar. I've used it many times for moving the entire /usr directory. but wouldn't trust it on / or /var (/var maybe -- but why if I can use dump/restore so quickly?). Best regards, Jack L. Stone, Administrator SageOne Net http://www.sage-one.net jackstone@sage-one.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message