[DM-MUG] HD FW Storage, RAID or other ideas...

Mon Oct 30 09:55:36 CST 2006

I intentionally left out 0+1 and 1+0 because they really work well  
for the server market, and not for consumers who want to get a lot of  
bang for their buck.

For your information though:

0+1 first stripes the drives (RAID 0) into two equal volumes, the  
mirrors the two volumes together.
RAID 10 (1+0) does the inverse- mirroring the drives before the  
striping.

RAID 10 is more fault tolerant, as one drive out of every mirror can  
fail without data loss.

-- 
Jon Thompson
jthompson at greatapetrust.org
515.360.1351

Insights through collaborations with apes
Great Ape Trust of Iowa
www.greatapetrust.org

On 2006, Oct 23, at 10:56 AM, Bryan Baker wrote:

> Good summary. Quick thought on (at least mirroring) A mirrored RAID  
> is NOT a Backup - it is a redundancy which can act as a sort of  
> backup against one or the other drives failing, but it is still not  
> a backup. I know you already made the point well, but I wanted to  
> add some emphasis.
>
> there are also a couple newer varieties that are gaining  
> popularity. 0+1 and 1+0 are variations (and I can't always remember  
> which is which) of striping plus mirroring and iirc use at least 3  
> drives (much like raid 5) which is generally a good compromise of  
> speed/storage and redundancy. I think in one scenario you have a R0  
> Striped array that is mirrored to a 3rd drive (or perhaps another  
> striped pair) and in another you have a mirror that is striped  
> across multiple drives.
>
> Now that I've put you all to sleep...
>
> On Oct 23, 2006, at 9:53 AM, Jon Thompson wrote:
>
>> Vicki,
>>
>> You may want to look at something such as a NAS (Network Attached  
>> Storage).  While it is not something I would recommend for most  
>> users, your storage needs are higher than most users, as well.  It  
>> also will be utilized by more and more users as storage needs  
>> increase.
>>
>> http://www.infrant.com
>>
>> You can get 2 TB (1.5 TB after RAID 5) for $2,339.  3TB (2.25 TB  
>> after RAID 5) is $3,139.
>>
>>
>> As for a short Primer on basic RAID so I am sure that you know  
>> what the RAID numbers mean...
>>
>> RAID 0 - "Striping"  -  Part of any given file is written to each  
>> drive.  _Very_ fast.  However, if you lose a drive you lose _all_  
>> of your data.  Not what you want.
>>
>> RAID 1 - "Mirroring" - Your file is written to both drives  
>> simultaneously.  You lose half of your storage (if you have two  
>> 500GB hard drives, they will appear as one).  If one drive dies,  
>> you still have the other.
>>
>> RAID 2,3,4 - not used, as they are less efficient or more costly  
>> than the other types of RAID.
>>
>> RAID 5 - "Striping with distributed parity" - Your file is written  
>> across all of the drives, except one.  On the extra drive, a  
>> parity bit is generated.  What the parity bit does is allow the  
>> data to be re-created if _one_ (and only one) drive fails.  RAID 5  
>> is computing intensive (which is why it is almost always done in  
>> hardware, with dedicated chips), but gives you almost all of the  
>> storage you pay for, without the risk with a single hard drive  
>> failure.  (Technically, the parity bits are distributed across all  
>> of the drives, as this increases throughput, but it is really  
>> unimportant to a layperson.)
>>
>>
>> In short, if you need pure speed for temporary data, use RAID 0.   
>> If you have two drives - mirror.  If you have more than two drives  
>> - RAID 5.
>>
>> Please note, RAID is also not a recommended solution for backup.   
>> It provides safety from hard disk failure.  However, it does not  
>> provide for user or computer errors.  If a file gets corrupt on a  
>> RAID, it will _not_ be recoverable, just as if it gets corrupt on  
>> a single drive.
>> -- 
>> Jon Thompson
>> jthompson at greatapetrust.org
>> 515.360.1351
>>
>> Insights through collaborations with apes
>> Great Ape Trust of Iowa
>> www.greatapetrust.org
>>
>>
>>
>> On 2006, Oct 23, at 1:58 AM, Victoria L. Herring wrote:
>>
>>> Thanks much for the links.  I'll check them out too...The idea of  
>>> a swappable batch of drives comes because I have a proliferation  
>>> of LaCies FW HDs all over my desk and not only is that clutter,  
>>> but it makes it hard to remember where to find things etc.   
>>> Aperture will let you have one library and portions over external  
>>> drives unhooked til you need them [apparently] which would be  
>>> perfect....more later as I research.
>>> -- 
>>> Victoria L. Herring, Attorney, Civil Rights, Discrimination &  
>>> Employment Law, <http://www.HerringLaw.com>;  Travel research,  
>>> planning & Photography, <http://www.JourneyZing.com>;  Des  
>>> Moines, Iowa, ph.515-255-4475.
>>> _______________________________________________
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>>
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>
> --
> Bryan Baker
> President
> Des Moines Macintosh Users Group
> http://www.dmmug.org
> president at dmmug.org
>
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