[CentOS] Re: software raid

Thu Mar 29 18:02:56 UTC 2007
Scott Silva <ssilva at sgvwater.com>

Manish Kathuria spake the following on 3/29/2007 10:29 AM:
> 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.
> Thanks,
It isn't so much a problem of performance, but if one drive on a channel dies,
it usually will lock the whole channel and stop the other drive on that
channel. If you swapped the secondary master and slave, you could lessen the
problems you might have. That way, if the secondary master died, taking the
secondary slave down with it until you remove the bad drive, you would still
have both arrays running (degraded, but running).


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