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two backups running at once is it harmful to data and / or the server

Posted on 2011-09-08
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Last Modified: 2012-05-12
On a SBS2008 I have a USB drive attached to the server and backups are run every night at 10:30PM. I'd like to schedule another backup to our offsite solution (nothing to do with the SBS2008 built in backup software) and know the initial backup may take some time, excess of 24 hours. My question is it harmful to have two backups running at the same time as the offsite backup overlaps the SBS2008 backup.
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Question by:WORKS2011
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by:cjrmail2k
ID: 36508564
Usually it won't be an issue as the offsite backup will only utilise your internet bandwidth (assuming it is under 100Mbps). If yuor network is running on Gbit then there is enough throughput for both a USB backup and a network backup. Note that it is always best to start the local (faster) backup first and let it run for around 30 minutes. THis will ensure that you are backing up different files rather than having the backups contending with each other for the same files.

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by:garycase
ID: 36508586
Harmful?   No.

... but it takes longer to run two backups at once than it does to run them sequentially, due to disk thrashing.   However ... in your scenario, that impact should be minimal, as the bandwidth of your offline backup is likely to be MUCH lower than the bandwidth of your disks.     I'd expect your normal 10:30 backup to simply take a bit longer than usual during the overlap period, but otherwise there's no real impact.
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by:noxcho
ID: 36508702
Actually depends on the answer to the question - are these two backups using the same Microsoft VSS technology? If yes then the data could corrupt due to simultaneous requests of VSS requestor.
Windows inbuilt backup solutions is using MS VSS definitely. So you need to find out if another one is doing the same.
And if VSS is not a problem then it should not be harmful. Sometimes if the process is too bulky you can get overflow of paging file and as a result BSOD on machine.
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by:andyalder
ID: 36510133
You have to make sure they don't both rely on the archive bit, if the MS backup resets the archive bit and the other backup relies on that for incrementals then you won't get all the files backed up.
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by:garycase
ID: 36510239
VSS correctly handles multiple simultaneous requests without deadlock, so that's not an issue.
As for the archive bit ... I doubt any modern backup utility relies on that these days.   If it did, a 2nd backup utility would never work correctly regardless of whether it was running simultaneously or not.
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by:marcustech
ID: 36512837
Note that it is always best to start the local (faster) backup first and let it run for around 30 minutes. THis will ensure that you are backing up different files rather than having the backups contending with each other for the same files.
Of course this only applies if you are using the same program to back up both sets.  The mistake is to assume that bothbackup utilities will crawl the data in the same order.
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by:BDithelp
ID: 36516973
You could possibly have issues depending on software your using, locking of files and what your actually backing up as well.

I like marcustech's 30 minute wait idea. If you going to run 2 backups stagger them as much as possible

Does your software support replication? You could avoid 2 backups by just replication the data to your cloud or offsite location from your first backup. No point in backing up the data twice but important to have that second copy offsite.

Do you own the remote site or are you cloud backing up? If you own it and it's close you could drive the usb drive over there an perform you initial backup then do incrementals on it after so you just writing the changes. If you cloud you can usually mail them a drive with the back to do you initial backup.

Sorry kinda need to know more about your software and setup to give you the best solution.
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by:marcustech
ID: 36517555

I like marcustech's 30 minute wait idea. If you going to run 2 backups stagger them as much as possible
It's not my idea, it's cjrmail2k's.  I don't actually agree with it - the only way to be totally sure that there are no conflicts is to run the backups consecutively, not concurrently.  Some proprietary backup products do take this into account when you configure multiple overlapping schedules and types of backup, and in this case I'd expect the software to handle it intelligently.
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by:WORKS2011
ID: 36519398
@cjrmail2k, @garycase your concerns with bandwidth make sense, the other concern is VSS. My understanding is two different backup software competing for MS VSS can cause the BSOD or compromise data integrity, your thoughts?

@noxcho I’ve experienced BCOD on a different machine using two different backup technologies sharing MS VSS and this is my main concern, glad you brought it up. I uninstalled the 3rd party backup software and never got the BSOD again. With the server I'm discussing in this thread the Microsoft built in solution uses MS VSS and the 3rd party backup solution does not use MS VSS (Acronis has the option to not use MS VSS). I haven’t run the two at the same time but may attempt to, do you think I’ll have problems? I’m thinking out loud now but maybe they already are because volume shadow copy is running on the SBS2008 server, so maybe all along it’s been backing up using MS VSS there and the offsite backup is running as well, am I correct to assume this? Your thoughts?

@andyalder you make a point but how do I confirm this?

@garrycase you write, “VSS correctly handles multiple simultaneous requests without deadlock, so that’s not an issue”, see my note above to @noxcho about the BSOD and my point about the local shadow copy running while the offsite backup is running means there isn’t a problem sharing the MS VSS, your thoughts on this? I guess to add to this could I turn back on the Windows Server Backup while the offsite backup is running.

Couple notes: 1. The offsite backup won’t take as long as it is now it’s only taking this long because it’s the first backup, once this is complete the incremental will be handled every night and will be allot smaller, 2. Software in this discussion is MS VSS, SBS2008 built in backup, and Acronis (note Acronis is configured to not use MS VSS technology).
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noxcho earned 500 total points
ID: 36524318
WORKS2011, I've seen such problems already personally. They happen mainly because the requests to the MS VSS service could be wrong. When using MS Backup the requests are the right one but third party tools could have such issues. When you see such problems then mostly it is a bug and should be reported to third party backup tool with fix request.
And sure the best way to avoid the problems letting run them one per time.
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by:WORKS2011
ID: 37192837
there was no BSOD but there was backup problems, the only way to resolve was to contact Acronis and they sent a fix. It was too time consuming, ended up dropping Acronis all together.
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