Comprehensive data protection for all workloads
Post Reply
mplep
Service Provider
Posts: 62
Liked: never
Joined: Sep 16, 2009 7:50 pm
Contact:

NtfsDisableLastAccessUpdate to reduce CBT?

Post by mplep »

Hi,

I'm looking at ways to reduce the amount of CBT on my Windows VM's. I've found a lot of discussions on the web regarding SAN snapshots and the NtfsDisableLastAccessUpdate registry value in Windows. I've also found a couple of posts on these forums as well. The general recommendation was to disable this feature as it can otherwise mark lots of blocks as changed even though they have just been opened and not actually modified.

Does anybody have knowledge or experience of this and whether is makes a difference?

Thanks

Mark

mplep
Service Provider
Posts: 62
Liked: never
Joined: Sep 16, 2009 7:50 pm
Contact:

Re: NtfsDisableLastAccessUpdate to reduce CBT?

Post by mplep »

Hi,

I just wanted to share an interesting result. I had a couple of VM's which were taking about 6hrs to incremental sync across a 100MB line which was not far off full sync times! I found that both these servers (Database/Exchange) had daily backups performed to local volumes. I moved these backups to dedicated volumes which I then excluded from Veeam. The result is both servers are down to about 35mins sync time now and have deltas about 1/5 the original size.

It seems obvious in hindsight, but as I didn't manage these SQL/Exchange backups I wasn't aware of their "backup folders" presence upon local volumes initially.

I don't have any results for disabling NtfsDisableLastAccessUpdate yet though.

Mark

folerx
Expert
Posts: 107
Liked: 8 times
Joined: Jun 22, 2016 9:47 pm
Full Name: Daniel Kaiser
Contact:

Re: NtfsDisableLastAccessUpdate to reduce CBT?

Post by folerx »

Any update on this?

Mike Resseler
Product Manager
Posts: 6324
Liked: 763 times
Joined: Feb 08, 2013 3:08 pm
Full Name: Mike Resseler
Location: Belgium
Contact:

Re: NtfsDisableLastAccessUpdate to reduce CBT?

Post by Mike Resseler »

Daniel,

Can you clarify. These previous posts are a few years old. Just for your information, there is no need to use this registry value. When we protect VMs, we are looking at block level changes and a last access update doesn't make the block change... Is this what you asked for?

Thanks

Mike

folerx
Expert
Posts: 107
Liked: 8 times
Joined: Jun 22, 2016 9:47 pm
Full Name: Daniel Kaiser
Contact:

Re: NtfsDisableLastAccessUpdate to reduce CBT?

Post by folerx »

Yes, tnx

dellock6
Veeam Software
Posts: 5940
Liked: 1758 times
Joined: Jul 26, 2009 3:39 pm
Full Name: Luca Dell'Oca
Location: Varese, Italy
Contact:

Re: NtfsDisableLastAccessUpdate to reduce CBT?

Post by dellock6 »

Well, actually "any" change at the vm level is a write IO that updates the underlying block, so there is a change. However, I agree those posts are 6 years old, so Daniel if you need any additional informatio, you'd better post here your use case so we may help.
Luca Dell'Oca
Principal EMEA Cloud Architect @ Veeam Software

@dellock6
https://www.virtualtothecore.com/
vExpert 2011 -> 2020
Veeam VMCE #1

Mike Resseler
Product Manager
Posts: 6324
Liked: 763 times
Joined: Feb 08, 2013 3:08 pm
Full Name: Mike Resseler
Location: Belgium
Contact:

Re: NtfsDisableLastAccessUpdate to reduce CBT?

Post by Mike Resseler »

Yes, as Luca says, a bit more information is needed. For example, starting from Vista (and I believe from 2008 R2) this registry is there by default and won't update it anymore.

Post Reply

Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 39 guests