Re: RAID 5 drive replacement schedule

[Adriel Desautels <adriel () netragard com>]

Nick,
	I agree with your interpretation and this is why I have issues with 
things like "CYA". The definitions that the "security industry" uses as 
a whole are not always clear and do not always define. PCI-DSS is just 
one example of many that do not clearly "define" what, how, who, when, etc.

I think that we, the "security industry" need to define things clearly 
so that the boundaries are fully understood. Availability with respect 
to security is a fuzzy boundary at best.

Isn't it the case that information being stored on a computer that has 
been shut down and is no longer available is secure? I think so, but 
that also depends on a lot of different things. Guess it also depends on 
how one defines secure doesn't it?

Regards,
        Adriel T. Desautels
        Chief Technology Officer
        Netragard, LLC.
        Office : 617-934-0269
        Mobile : 617-633-3821
        http://www.linkedin.com/pub/1/118/a45

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Nick Vaernhoej wrote:
> Philippe,
>
> Any chance this is a bit up to interpretation?
> If you build a box with no access the inside is for the sake of argument "safe".
> If you add a door it is available, but only as far as the architect is concerned.
> If you add a lock to the door and lock it, the inside is once again "safe".
>
> Here is my interpretation of the availability topic, when you give the key to the users of the box you have ensured 
> availability as it applies to security.
>
> Let me know if I am way off :-D
>
> Nick Vaernhoej
> "Quidquid latine dictum sit, altum sonatur."
>
>
> > -  -----Original Message-----
> > -  From: listbounce () securityfocus com
> > -  [mailto:listbounce () securityfocus com] On Behalf Of Rivest, Philippe
> > -  Sent: Friday, June 20, 2008 12:24 PM
> > -  To: Adriel Desautels; Murda Mcloud
> > -  Cc: security-basics () securityfocus com
> > -  Subject: RE: RAID 5 drive replacement schedule
> > -  
> > -  Adriel & Murda
> > -  
> > -  It is a security issue the way you store your data. In regards to the
> > -  raid
> > -  technologies, raid 5 improves the availability of the data by making
> > -  sure
> > -  that a single drive failed will not impact the availability of the
> > -  data.
> > -  
> > -  Remember that security is
> > -  1- Confidentiality
> > -  2- Availability
> > -  3- Integrity
> > -  
> > -  The main goal of a Raid 5 is to help #2. You are referring to the
> > -  disposal of
> > -  the HD which is the issue of confidentiality and that is not what
> > -  Murda was
> > -  aiming at. If it is, go for encryption, degaussing, destruction and
> > -  just
> > -  plain format (if the data is not confidential).
> > -  
> > -  As I explained to him offline, the MTTF and MTBF is about the same
> > -  for 2 HD
> > -  bought/constructed at about the same time. How ever, those are not
> > -  absolute
> > -  numbers that state that, if one drive fails the other one is about to
> > -  go too.
> > -  It's more an estimated value against which you should have some
> > -  confidence/hope, your drive should not fail before X hours (it could
> > -  go
> > -  before but the average is X).
> > -  
> > -  In a raid 5, Drive A, B and C are online and working (they are the
> > -  same drive
> > -  bought at the same time). Drive A fails, you should NOT change drive
> > -  B & C
> > -  unless they are failing also. If you do, the cost of your raid 5 will
> > -  be
> > -  greater then what it should be (the replacing of the parts are going
> > -  to cost
> > -  a lot). Change drive A and hope drives B & C will last longer.
> > -  
> > -  
> > -  The only issue is that 2 drives fail at the same time, which is very
> > -  improbable. And if it does, you should be going for your back ups.
> > -  
> > -  
> > -  I do hope this clarified the questions and that I wasn't to unclear
> > -  with my
> > -  details!
> > -  
> > -  Merci / Thanks
> > -  Philippe Rivest, CEH
> > -  Vérificateur interne en sécurité de l'information
> > -  Courriel: Privest () transforce ca
> > -  Téléphone: (514) 331-4417
> > -  www.transforce.ca
>
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