Re: Is there an issue with turning off "scrubbing free RAM" on boot with Xen 4.1.3

[Andrew Cooper <andrew.cooper3@citrix.com>]

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On 09/10/13 19:24, Roddy Rodstein wrote:
>
> Greetings,
>
>  
>
> Thank you in advance for your support!
>
>  
>
> Our HP Xen 4.1.3 servers have 1TB of RAM, each Xen servers take 20
> minutes to boot largely due to the "scrub free RAM" phase. If/when we
> have dom0 failures and HA kicks-in, we would like to reduce the boot
> time to make the resource quickly available, perhaps using the
> no-bootscrub attribute in grub.conf.
>
>  
>
> Could you please share your comments about turning of RAM scrubbing,
> i.e. have you seen any consequences, security issues and/or threats,
> red flags, etc...?
>
>  
>
> We have asked the same question at the commercially supported Xen
> forums, i.e. Oracle and Citrix, as well as to each aforementioned
> support team, and have not received a lick of meaningful information.
>
>  
>
> Respectfully,
>
> Roddy
>

In the Xen model, domains are responsible for clearing any sensitive
data they have out of memory before shutdown.

The bootscrub is a preventative measure to ensure that after a crash,
stale domain information is cleared from RAM before that RAM is reused
for a new VM.

If this is not a concern for you, then you can easily turn bootscrub off
by adding "no-bootscrub" to the Xen command line.

~Andrew

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