[AccessD] Google's Disk Failure Experience

Michael Bahr jedi at charm.net
Wed Jul 21 12:42:29 CDT 2010


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
>
> --
> AccessD mailing list
> AccessD at databaseadvisors.com
> http://databaseadvisors.com/mailman/listinfo/accessd
> Website: http://www.databaseadvisors.com
>





More information about the AccessD mailing list