[AccessD] Google's Disk Failure Experience

Michael Bahr jedi at charm.net
Thu Jul 22 11:30:55 CDT 2010


If the media content is not reproducible then it is a no brainer.

Mike...

> I have to question whether the overhead of taping / cutting commercials
> doesn't reduce your savings
> quite a bit.  As you asked me, how much time and how do you value your
> time.
>
> But that is a whole nother discussion.
>
> John W. Colby
> www.ColbyConsulting.com
>
>
> Michael Bahr wrote:
>> Well, I can see your point that only ripping DVD's takes 2 minutes each
>> and you do not need them anymore.  But for me I record OTA/cable HD
>> shows
>> and uncut movies and cut out the commercials and archive them.  Now I
>> have
>> whole seasons worth of shows and movies.  I save money buy not buying
>> the
>> Blu-Ray disks ($30-$60 for each season or movie).  So yes it is
>> important
>> to me to have a backup as these are not reproducible.  A seperate media
>> server setup as raid 1 does fit my needs.
>>
>> Mike...
>>
>>>  >How much is your time worth?
>>>
>>> This is a classic case of insufficient analysis...
>>>
>>> The cost is not the cost of the drive.  It is the cost of the drive
>>> (twice
>>> the drives), plus the
>>> cost of the SATA ports (twice) plus the cost of the power supply (twice
>>> the disk current - 12v),
>>> plus the cost of electricity to run the disks (twice the electricity)
>>> plus
>>> the cost of a case big
>>> enough to handle enough drives (twice as large disk cage) plus...
>>>
>>> Of course all my "twices" are on a "per disk used" basis, not a total
>>> system cost and I understand
>>> the difference.
>>>
>>> Furthermore, my time isn't the cost of my time to rip 200 dvds, it is
>>> the
>>> cost of my time to rip 200
>>> dvds divided by the probability of losing 2 disks at the same time.
>>>
>>> I ripped my drives as I wanted to watch them, so it was an incremental
>>> cost accumulated over time.
>>> The actual time is about 2 minutes per dvd.  200 dvds per drive is an
>>> actual cost of 200 minutes to
>>> fill a drive.  Would I actually rerip all of the disks?  No because
>>> many
>>> of them are for my kids who
>>> are now older and don't even watch those disks any more, not to mention
>>> the disks I ripped that I
>>> just don't care about.
>>>
>>> HOWEVER... In the two years that I have been using the system, I have
>>> never lost one of these
>>> drives.  Thus my time to "do it over again" is zero (so far).  I have
>>> been
>>> working with raid
>>> extensively for about 5 years, and in those 5 years I have lost single
>>> drives but I have never lost
>>> two drives at the same time.
>>>
>>> I am sure that there are numbers out there that discuss the probability
>>> of
>>> two drive failures.  In
>>> fact IIRC from that paper by google, the probability of failure of any
>>> given single drive over 5
>>> years was about 14%?  The probability of two failures (my simple math)
>>> would be .14 * .14 = .0196 or
>>> ~ 2%.  That is for two failures, NOT two SIMULTANEOUS failures.
>>>
>>> All of this matters if the cost is catastrophic.  Facing a 2% chance
>>> that
>>> I will have to re-rip 200
>>> dvds in any given 5 year period, I am unwilling to commit the extra
>>> money
>>> to preventing this
>>> possibility.
>>>
>>> This whole discussion does point out that an analysis of the actual
>>> numbers might cause one to come
>>> to a different conclusion.  And who knows, you might decide "screw the
>>> costs", it is worth it to me.
>>>
>>> It is not worth it to me.
>>>
>>> Look at Unraid.
>>>
>>> http://lime-technology.com/
>>>
>>> I am not trying to sell anyone on unRaid, I am simply saying consider
>>> it
>>> for a specific class of
>>> redundancy needs.  For this level of redundancy need, unRaid seems like
>>> a
>>> good compromise.
>>>
>>> John W. Colby
>>> www.ColbyConsulting.com
>>>
>>>
>>> Michael Bahr wrote:
>>>> John, for your media collections you really should go only Raid 1.
>>>> Yeah
>>>> if you lose the HD you can re-do everything but who has the time?
>>>> Besides
>>>> 2TB HD's are ~<$150 or so.  How much is your time worth?
>>>>
>>>> Mike...
>>>>
>>>>> I am about to build an UnRaid for my massive video / music
>>>>> collection.
>>>>> I
>>>>> currently have no
>>>>> protection on that so if I lose a disk I lose all of that on one
>>>>> disk.
>>>>> With Unraid I
>>>>> would have "raid 5 like"
>>>>> storage so that in the event of single drive failure I can still
>>>>> recover.
>>>>> If I do lose it I just
>>>>> re-rip.  Not the end of the world but not something I want to do.
>>>>>
>>>>> John W. Colby
>>>>> www.ColbyConsulting.com
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>>> Website: http://www.databaseadvisors.com
>>>
>>
>>
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