D2D2504i G1 changing block size

[Simon Powell-IT Helpdes]

In reading the D2D best practices guide, I see it recognises a block size of 256K for the backup software. Our Backup Exec 2010R2 media server currently has the block size set at 64k for each virtual drive. It seems sensible to increase this to 256k. However, what will happen to the backups that are taken following this. Will the D2D2504i be able to dedupe this data with respect to the previous backups done at 64K, or will it treat it as different data.

[Eric de Lange (MSE)]

Hi Simon,

The D2D uses a much smaller blocksize to deduplication on. From a deduplication perspective there would be little impact.

changing the blocksize in BackupExec may require you to reformat your (virtual) media through.

From a performance perspective, you may see an improvement in backup throughput although performance is dependent on a lot of other factors in the environment.

best regards,
-Eric

[Simon Powell-IT Helpdes]

Ok. Sounds like it wouldn't be worth the effort. I'll concentrate on our network issues first.

[Dave Dewar]

Simon,

The advice in the best practices guide regarding increasing block size is really focussed on ISV applications that have a self describing format and insert unique data into every block. This unique data will impact deduplication ratio and performance and so reducing the frequency of this by increasing block size can provide a significant benefit.

Symantecs Backup Exec and Netbackup do not fall into this category and hence changing block size for these applications has very little benefit within the D2D appliance in terms of dedupe ratio and performance. However, it might be of some benefit performance wise upstream of the D2D.

Cheers,

Dave Dewar