Re: RAID 5 drive replacement schedule

[Adriel Desautels <adriel () netragard com>]

Philippe,
	I disagree with you and I think that the definition of security that 
you provided is partial, but thats just my opinion. Availability is a 
vague term that can, but does not always have a role in security. 
Determining what the proper schedule is for a drive replacement policy 
is something that can be done by IT without the security team. Deciding 
how to dispose of the drives on the other hand is security.


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

        Join the Netragard, LLC. Linked In Group:
        http://www.linkedin.com/e/gis/48683/0B98E1705142

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Rivest, Philippe wrote:
> 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
>
>
> -----Message d'origine-----
> De : listbounce () securityfocus com [mailto:listbounce () securityfocus com] De la
> part de Adriel Desautels
> Envoyé : 20 juin 2008 11:27
> À : Murda Mcloud
> Cc : security-basics () securityfocus com
> Objet : Re: RAID 5 drive replacement schedule
>
> Murda,
> 	The real answer to your question is that it is very, very improbable 
> that all of the drives in the array will fail at the same time. Most 
> drives are good for a certain period of years, after which point you are 
> getting "extra time".
>
>         That is not a security issue though. That is an IT related issue. The
>
> security issue comes into play when you dispose of your drives. Do you 
> shred them, just throw them in the dumpster, how do you dispose of them?
>
>         
> 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
>
>         Join the Netragard, LLC. Linked In Group:
>         http://www.linkedin.com/e/gis/48683/0B98E1705142
>
> ---------------------------------------------------------------
> Netragard, LLC - http://www.netragard.com  -  "We make IT Safe"
> Penetration Testing, Vulnerability Assessments, Website Security
>
> Netragard Whitepaper Downloads:
> -------------------------------
> Choosing the right provider : http://tinyurl.com/2ahk3j
> Three Things you must know  : http://tinyurl.com/26pjsn
>
>
> Murda Mcloud wrote:
> > In my mind, this a security related question as it has to do with ensuring
> > availability.
> >
> > Does anyone have links towards any whitepapers etc that suggest replacement
> > of disks in a RAID 5 array as part of a maintenance cycle?
> >
> > If all the drives in an array are the same age and one fails; does this
> mean
> > the others are more likely to fail. I'd imagine so as they have had the
> same
> > amount of usage.
> >
> >
> >
> >
> >
> >