Date: Sun, 29 Dec 2002 01:11:37 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Patrick Cable II <freebsd@slaudiovis.org> Cc: chat@freebsd.org Subject: Re: Backup Solutions Message-ID: <3E0EBC49.86AD7E28@mindspring.com> References: <3E0DC536.8010001@slaudiovis.org>
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Patrick Cable II wrote: > What do you use for a backup solution for your freebsd server? Depends on what problems you want to solve. There are at least 4 major ones: 1) Recovery following single point of failure 2) Recovery following fire 3) Recovery following accidental deletion 4) Recovery following malicious corruption (e.g. virus/worm/etc.) 5) Permissable recoverability latency A replicated server saves you from #1. It can also save you from #2, if you don't locate the replica at the same site. It does nothing for #3 or #4, since the deletion and/or damage is copied to your replica. It addresses #5 only if your software cooperates, a lot (e.g. you can lose a day of data, if the replication can't happen against open files, i.e. MSDE, MS Access, etc.). A tape backup or DVD-RAM addresses #1, #3, and #4. It probably fails to address #5, completely. It may or may not address #2, depending on how you set up your policies and procedures, and whether or not you follow them religiously (e.g. offsite storage). DVD-RAM has the same problems as a replica. DVD-ROM adds support for #3 and #4, at least for as long as your discard period lasts. DVD-RAM can do this, too, but you have to treat it as DVD-ROM, to the extent of having to take the media physically to another machine to erase it: if you don't, then anything that can happen to a disk can happen to it. A USB hard drive is basically just a disk. Same effects as a second server, except you can (maybe) address #2, by taking it off site and/or locking it in a fire safe. You could also add: 6) Permissable recovery latency This is different from #5: #5 deals with how much change you are willing to lose (e.g. with an accounting system, are you willing to have to repeat the days payment postings), and #6 is all about how long it takes to get back up, following a catastrophe. Consider also: if it's OK to have to repost payments (as an example), what are you going to do about the fact that the documents from which the postings are being made burnt in the same fire that ate your server? You can't post checks that you can't deposit/haven't deposited, and which are now ashes. I expect that the correct thing to do is to have a replica and a non-volatile backup mechanism, in combination. I also suggest that you avoid the "active file can't be backed up" problem, by choosing the correct software (and no, "snapshots" are not good enough, because they don't trap the right state for the implied metadata, among other deficiencies). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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