[CentOS] Re: software raid

Thu Mar 29 17:47:11 UTC 2007
Les Mikesell <lesmikesell at gmail.com>

Manish Kathuria wrote:
> On 3/29/07, tblader <tblader at flambeau.com> wrote:
>> One drawback is software raid wants a single ide device on each ide 
>> channel.
>> This means buying an ide card (if you want more than two devices) 
>> which doesn't
>> always play well with the rest of the system (4+ ide devices).  Some 
>> mainboards
>> might have more than two ide channels, but I just opted for the cheap 
>> ide card.
> Can you please confirm the same or refer to some documentation
> indicating that ? I have recently added two HDDs as the slave devices
> on Primary and Secondary IDE channels configured as software raid
> devices where the two master devices on these IDE channels were
> already being used for  software raid. Now I have 4 devices on two IDE
> channels with partition pairs configured as RAID-1 devices. So far all
> the raid devices are working fine though I do expect a deterioration
> in performance because of 4 devices on two channels.  I would like to
> reconfirm if  "single ide device on each ide channel" is true for
> software raid. Comments please.

It is just a performance issue, at least on hardware that works as 
intended.  IDE controllers can only issue one command at a time so you 
can't even overlap waiting for the seeks to complete on two drives on 
the same cable - but it won't break anything.

   Les Mikesell
    lesmikesell at gmail.com