Host-based backup of VMware vSphere VMs.
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Full Name: Mike Myers

Question about Deduplication

Post by 33014 »

Hi there,

I have read the FAQ about deduplication but I am still confused. After installing Veeam Backup & Replication 6 I attached a vmdk to the Veeam VM. This has been configured as deduplication store. So I created a new backup job of 11 similar VMs. They are all pretty much identical insight. Each is about 330MB in size.

After I checked the backup I can see that about 2.859GB have been written to the deduplication store. Why? I would have expected it to be maybe 500MB or similar, but certainly not 2.8GB.

To me it appears as if deduplication didn't happen, only compression

Here is the summary of the job.
Success 11 Start time 10:21:49 Total size 220.0 GB Backup size 2.7 GB
Warning 0 End time 10:39:58 Data read 220.0 GB Dedupe 100.0x
Error 0 Duration 0:18:09 Transferred 2.7 GB Compression 1.1x

The 11 VMs are all thin disks. The "Used Space" is shown in the vSphere Client with 3.636GB.
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Re: Question about Deduplication

Post by Gostev »

Based on this results it looks like your VMs are not similar at all (meaning, there are almost no identical virtual disk blocks). Similar VMs (such as made from the same template) dedupe exceptionally well - overall data reduction ratios (compression + dedupe) are very close to those provided by hardware deduplicating storage appliances. Thanks.
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