The relation between OSR and dedup & compression

[baber]

I am using vsan 7 update3 and AFA

1- Do I have to use OSR=100%  if I want to use dedup & compression ?

2- Do I have to use OSR=100% if I want to use just compression ?

3- Which type of OSR is more useful if I want use dedup & compression ( more dedup and compression ) ?

4- Which type of OSR is more useful if I want to use just compression ?

BR

[IRIX201110141]

https://kb.vmware.com/s/article/52839

It looks like that OSR should be set to 0 if you would like to receive best from the DataReduction.

Regards,
Joerg

[TheBobkin]

@baber You don't "have to use" OSR=0 or OSR=100 but it depends whether you want to save space with dedupe and/or compression here or not - if you have OSR=100 set on an Object, even if blocks from it can be dedupe and/or compressed, it won't save you any space as the entire space for the Object has to be reserved (because that is what you told it to do). 

So, if you want to maximise possible space savings from dedupe and/or compression then use OSR=0.

[baber]

Thanks but as I want use dedup or compression so must set OSR=0 or 100 but according to this KB : https://kb.vmware.com/s/article/52839

1- recommendation is use OSR=0 to increase dedup or compression ratio . Is that correct ?

2- but this mentions just for vsan 6.6 and before that . Does it also about vSAN 7 U3 ?

3- Disadvantages of using OSR=0 is we may surprise for vmdk size and cannot monitor it 

[baber]

Would you please help me about it ?

[depping · Accepted solution]

You don't set OSR at all! If it is not configured it is "0". This is what you need to take advantage of deduplication and compression. So just to be very specific:

1) the recommendation is to NOT configure OSR at all, which means that it is set to 0.

2) yes, it applies to all CURRENT versions of vSAN, that includes 7.0 U3

3) this means that when OSR=0 that no capacity is reserved indeed, and you will need to monitor used/unused/provisioned to avoid a situation where you end up without unused capacity.