[Ham-Mac] Re: Ham-Mac Digest, Vol 24, Issue 8

[David Ferrington]

By RAID I mean 
Redundant Array of Independent (or Inexpensive) Disks, a category of disk
drives that employ two or more drives in combination for fault tolerance and
performance. RAID disk drives are used frequently on servers but aren't
generally necessary for personal computers.
(see http://www.webopedia.com/TERM/R/RAID.html)

Basically a number of disks that each take a part of the data and one disk
that takes some form of checksum or parity bit (some for of encoded
information) that means if one of the disks fails, the whole system will
just carry one without any problem (as long as another disk doesn't fail).
You can then 'hot-swap' the failed disk and the RAID device will bring the
new one up to date with all the information using the other disks and the
checksum. Sounds expensive? It is.

It would also be possible to do this with a 'true' mirror where everything
written to one disk is written to another at the same time, but normally if
one fails, there isn't a seamless switch over to the other. You really need
RAID if you want true fault tolerance that means the CPU does not even know
one of the disks has failed


By rotating the hard drives - one of the backup drives is an Iomega Peerless
20GB removable Firewire drive - it is a 'cartridge disk' that plugs into a
dock - I swap them each week so the back is writen to a different disk ,
therefore I have the current weeks backup and the previous weeks backup.


On 10/1/06 9:00 am, "ham-mac-request at mailman.qth.net"
<ham-mac-request at mailman.qth.net> sent:
> Message: 1
> Date: Mon, 09 Jan 2006 07:59:14 -0500
> From: Todd Ruby <rubywine at verizon.net>
> Subject: [Ham-Mac] Re: Ham-Mac Digest, Vol 24, Issue 7
> To: ham-mac at mailman.qth.net
> Message-ID: <019cbab190e2d14ce96dce793adfdb25 at verizon.net>
> Content-Type: text/plain; charset=US-ASCII; format=flowed
> 
> David
> what do you mean by RAID?
> can you explain what you mean by rotating one of the hard drives?
> 
> I appreciated the detail of your post.
> 
> thanks
> 
> 
> 73
> de
> todd
> WB2ZAB
> 
>> As I see it, there are at least the following reasons for backing up:
>> 
>> + to project against a HD failure
>> - backup to another HD, if the data is very dynamic and its business
>>   critical, use RAID
>> = I use 2 HD's, one is removable and gets rotated every week, so I
>> have two
>>   weeks worth, the other is a LaCie 500GB d2 (just purchased to replace
>>   smaller HD, I've run out of space) - this reduces the risk of
>> failure to
>>   a figure smaller than that of me getting to be a Space Station Ham
>> :-)
>>   This does my MLDX log etc, basically my Documents/Library/Readerware
>> db
>>   etc. and the current years (2006) iPhotos.
> 
-- 
There is no pillow so soft as a clear conscience. -French proverb