topic Re: SME LUNS & Fractional reserve in ONTAP Discussions

SME LUNS & Fractional reserve

tyeoman_swinton — Thu, 05 Jun 2025 07:28:28 GMT

Hi,

Has anyone got any steer if it is still required that the volume is 120% bigger than the LUN(S) it contains for Exchange? We're migrating Exchange to our NetApp very shortly and I'm trying to ensure we use storage as efficiently as possible. Of course if we do a defrag then we would have to turn off snapshots but I'm sure our data rate of change will not be great enough to need this level of write protection.

Does anyone out there reduce their fractional/snapshot reserves and use auto delete/grow instead? If so how do people find this works with SME?

Thanks in advance for any feedback,

Trevor

Re: SME LUNS & Fractional reserve

anthonyfeigl — Thu, 07 May 2009 17:24:25 GMT

Hey Tervor,

I have to admit I am not familiar with Fractional Reserve, but Chris had a great Blog recently on the subject.

http://communities.netapp.com/groups/chris-kranz-hardware-pro/blog/2009/03/05/fractional-reservation--lun-overwrite

Check it out.

Hope it helps.

Anthony Feigl

Re: SME LUNS & Fractional reserve

pascalduk — Fri, 08 May 2009 06:11:23 GMT

Our exchange 2007 environment is running with 20% frs and volume/lun guarantees on. We have setup SME to delete all snapshots except the last one when 70% of the frs is actually used and dismount the databases at 90%. We do not use vol autosize on the filer.

The 20% frs was a very conservative estimate allowing about 2 days of block changes even after the volume is full, so we will probably go even lower in the future.

Re: SME LUNS & Fractional reserve

tyeoman_swinton — Fri, 08 May 2009 06:36:00 GMT

Thanks Anthony & Pascal. It's great to do a sanity check on these things.