Reversed Incremental or Synthetic Full

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Reversed Incremental or Synthetic Full

Veeam Logoby AndyR » Tue Nov 09, 2010 11:56 pm

HI All,

Recently upgraded to Veeam V5 and have a question on backup modes.

Currently run Veeam from a dedicated VM so have all backup jobs running in Virtual Appliance mode direct to an NTFS volume on the iSCSI SAN. Recently the backups have been growing each night so very soon I'm going to hit a bit of a space crunch, so I would like some advise on backup modes.

All our jobs at the moment run in Reversed Incremental. Each night the NTFS volume with the Veeam backups on is also dumped to tape (Backup Exec with a windows share on the Veeam server) and works fine.

Would I be better of switching to Incremental and then have a Synthetic Full run on Saturday? What I'm looking to achieve is less space being used by all the backups if at all possible? If I change it to this for one of the jobs as a test, will it risk my current backups that are there?

Thanks,

Andy
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Re: Reversed Incremental or Synthetic Full

Veeam Logoby tsightler » Wed Nov 10, 2010 2:41 am

I think it's a little hard to answer because I'm not 100% sure where you are attempting to use less space, disk or tape and you provided no information about your incremental sizes and your disk retention requirements.

As a general rule, reverse incrementals are going to use the least amount of space on disk, but the most amount on tape, while the reverse is true of forward incrementals, they will use more disk space, but significantly less tape space. The only exception might be if you have a fairly small retention period.

Assume you have a 100GB full backup with 10GB of changes a day, here's how the space would break down assuming 4 weeks retention:

Reverse Incremental:
Disk -- 100GB Full + 280GB (10GB/day * 28 days) of reverse incrementals = 380GB
Tape -- 100GB VBK copied to tape every day * 28 days = 2.8TB

Forward Incremental w/Synthetic Full:
Disk -- 400GB (100GB Full * 1 per week) + 240GB (10GB/day incrementals * 24 days) = 640GB
Tape -- Same as disk, since you simply copy the full or incremental to tape every day = 640GB

So, the Forward Incremental/Synthetic option in this scenario would use ~70% more disk space, but less than 25% of the tape space. If you're planning to keep only a short period of disks on retention and use tape for long term storage then forward incrementals will save space, but that's about the only scenario where it will save space. For the best space savings with on disk retention, reverse incremental are the way to go, but at the cost of a large amount of tape space.
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Re: Reversed Incremental or Synthetic Full

Veeam Logoby lewislampkin » Wed Nov 10, 2010 3:58 pm

AndyR wrote:Currently run Veeam from a dedicated VM so have all backup jobs running in Virtual Appliance mode direct to an NTFS volume on the iSCSI SAN. Recently the backups have been growing each night so very soon I'm going to hit a bit of a space crunch, so I would like some advise on backup modes.

All our jobs at the moment run in Reversed Incremental. Each night the NTFS volume with the Veeam backups on is also dumped to tape (Backup Exec with a windows share on the Veeam server) and works fine.


Andy


Andy, such a cool idea. I was wondering how to handle getting my jobs sent to tape, and you pasted an elegant solution.

I'm trying to follow your steps here, please correct me ...

Did you first make a volume on the SAN, then connected it to your VEEAM server, and formatted it as NTFS within Windows?
After that, your Veeam does the backup locally, and places it on the NTFS volume local to itself.
Then, you share that volume from your Veeam server.
Then, your Backup exec backs up that volume through Windows ...

Is that your trick?

My question was how this would affect eventual migration to using "Replication" but it wouldn't matter, as long as the source saw the files, it could send them to the target, right?

I'm just trying to get this clear in my head.

Thanks.
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Re: Reversed Incremental or Synthetic Full

Veeam Logoby joergr » Wed Nov 10, 2010 6:31 pm

Me personally i prefer reversed incremental because my main strategy is to get a full working backup to tape every night without the need to merge increments when in an emergency need to get my files back from tape. Even with new naming logic of b+r5 this can easily done with various backup-to-tape products.

Check out this
viewtopic.php?f=2&t=5396

and this
viewtopic.php?f=2&t=5387

best regards,
Joerg
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Re: Reversed Incremental or Synthetic Full

Veeam Logoby Gostev » Wed Nov 10, 2010 7:42 pm

Just wanted to chime in and add that I have a document in sticky FAQ topic which may help in choosing best backup mode to use in each specific scenario.
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