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Re: RAID 5 drive replacement schedule
From: Adriel Desautels <adriel () netragard com>
Date: Fri, 20 Jun 2008 16:26:10 -0400

Philippe,
Alright forgive me, I was being too binary. With that said, I think that watching for drive errors is most probably the best way to go (that was in an earlier post from someone else too). I'm sure that there are software technologies that monitor for "Failing drive errors", but I'm not sure what they are.

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


Rivest, Philippe wrote:
I do think we are saying just about the same thing. But I may of not be clear
so let me restate.

Raid 5 is an IT field & technologie, and adds to the security by making 1
failed drive NOT impact availability. That's all I meant. No decision or
security implication should be done before or after that (unless theres an
incident). No security team should be implicated in the drive replacement as
this is normal IT operation.
Raid 5 helps security in keeping the data accessible in the event of a failed
drive.

Side note:
For my CAI is always security related and justified. Make it high or low
availability it is security and has to be justified.

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 : Adriel Desautels [mailto:adriel () netragard com] Envoyé : 20 juin 2008 14:00
À : Rivest, Philippe
Cc : Murda Mcloud; security-basics () securityfocus com
Objet : Re: RAID 5 drive replacement schedule

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

---------------------------------------------------------------
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


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.






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