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trichert
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Reversed vs Normal, Processing Time

Post by trichert » Jun 08, 2011 1:06 pm

Our setup is fairly simple. We have a 3 Host ESXi 4.1 cluster connected via 8GB FC to a Compellent SAN.

We have a physical backup server also connected via 8GB FC to the SAN. The physical server has a 12 TB SATA RAID-5 store for physical backups. Running B&R 5.02

We wanted to use reversed incrementals so that every day we had a full and could just write that to tape, simple and sweet. But with that setup B&R seems to have to re-write the backup files in entirety every night, so for example if we have a 5TB backup file with 50 gigs of changed data, because the way reversed incrementals work it is having to beat 5TB of data on the local disk even though only 50G changed. Is there anyway around this ? Because it is not able to complete this process so we have had to modify our strategy and do this :

Incrementals every day, with a synthetic full created during Friday's backup which completes by midday Saturday, which is then dumped off to tape in time for us to send off site on Monday. The process mostly works but there is no margin for error since everything is occuring on a weekend. It would be really nice if there was a way for the reversed incremental to not have to re-write all of the data every night ..

Vitaliy S.
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Re: Reversed vs Normal, Processing Time

Post by Vitaliy S. » Jun 08, 2011 2:49 pm

trichert wrote:But with that setup B&R seems to have to re-write the backup files in entirety every night, so for example if we have a 5TB backup file with 50 gigs of changed data, because the way reversed incrementals work it is having to beat 5TB of data on the local disk even though only 50G changed. Is there anyway around this ?
Every time a reversed incremental backup job runs it updates existing VBK file with VM changes and creates a new rollback (VRB file). Could you please clarify why this approach doesn't work for you?
trichert wrote:Incrementals every day, with a synthetic full created during Friday's backup which completes by midday Saturday, which is then dumped off to tape in time for us to send off site on Monday. The process mostly works but there is no margin for error since everything is occuring on a weekend. It would be really nice if there was a way for the reversed incremental to not have to re-write all of the data every night ..
I'm not sure I follow you here. Reversed incremental is designed to update existing VBK file (latest VM state) with recent changes, it doesn't re-create it from scratch. If you want to offload your backup files to tape then forward incremental mode should be a way to go.

trichert
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Re: Reversed vs Normal, Processing Time

Post by trichert » Jun 11, 2011 8:16 pm

This is not what I am seeing. When my reversed incremental runs, it re-writes the entire vbk not just updating it.

Vitaliy S.
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Re: Reversed vs Normal, Processing Time

Post by Vitaliy S. » Jun 13, 2011 8:31 am

Todd, could you please clarify it further? How do you determine that the VBK file was completely re-written? Please note that the only way to create a new VBK file is to schedule a full run.

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Re: Reversed vs Normal, Processing Time

Post by trichert » Jun 13, 2011 12:22 pm

Lets say a backup that is configured for reverse incremental is 1TB and has 10GB of delta for a day. When the backup runs I see 1.01TB of data being written to the disk, not 10GB.

Vitaliy S.
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Re: Reversed vs Normal, Processing Time

Post by Vitaliy S. » Jun 13, 2011 12:45 pm

Please have a look at the blog post Veeam Synthetic Backup Explained and our User Guide (page 12) for the reversed incremental backup mode explanation. Hope this helps.

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