RE: Re: OT Raid Setup for MP3 Server

["Mark Harrison" <Mark.Harrison@xxxxxxx>]

Paul,

RAID 5 uses both mirroring and striping, but more intelligently than simply
applying them separately (ie - RAID 1+0), to give less wastage.

Red herring on the "both Audiotrons need to play the _same_". In
fact, when the _first_ reads the track, it will be read off disk into
server RAM. It's the RAM copy that's sent over the network.

When the second reads it, it will use the copy in RAM already, and not
require a second disk access.

If you have N disks, each of capacity A, then the capacity of the RAID
array is (N-1) x A. 

eg - 4 disks, each of capacity 120Gb. RAID5 capacity = (4-1) x 120 = 3 x
120 = 360Gb

I don't quite follow how you can use 2 off, 80Gb and 1 off, 60Gb in a pure
RAID 5.

Regards,

Mark

-----Original Message-----
From: paul_watkin [mailto:paul_watkin@xxxxxxx]
Sent: 29 April 2002 12:08
To: ukha_d@xxxxxxx
Subject: [ukha_d] Re: OT Raid Setup for MP3 Server


>from
but how do you work out what the logical drive capacity is likely to 
be?

My original reason for the mirroring 0+1 solution was to be able to 
string a number of Audiotrons off the server and make sure I don't 
get any issues with file access if two Audiotrons want to play the 
same track? Objective being very basic zoned audio before spending 
shed loads on the ELAN system

On the Audiotron tack, does anyone have any experience of buying them 
from  htttp://www.thenerds.net , or know of a company who will ship
to an address other than cardholders?

Cheers

Paul
--- In ukha_d@y..., "graham_howe" <graham@s...> wrote:
> Forgive me for hijacking this thread for personal use, but I have a
> question about raid 5 so I thought I'd add it here rather than 
start 
> a new topic.
> 
> I have recently rebuilt my server with a raid 5 contoller and 3 hot
> swap drives. The drives are 2 x 80 and 1 x 60 so my logical disk is
> 140Gb. With disk prices falling quite dramatically, I thought that
I 
> would take the opportunity to upgrade, but I don't want to 
completely 
> rebuild the server.
> 
> My understanding is that if I simply remove one disk and replace it
> with another, then the system will automatically 'sync' the new 
disk 
> so that everything is hunky dorey again. If that is the case, then
> can I simply replace one disk at a time (allowing time for 'sync')
> until I achieve my desired configuration.
> 
> A few points concern me, first is it OK for a disk to be replaced 
> with a larger one. Second, is it possible to add additional disks 
to 
> the array (although they will have to be fixed as I have no more 
5.25 
> bays for hot swap caddies) without rebuilding.
> 
> Regards
> 
> Graham



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