[ILUG] Soft Raid - Hard Controllers

[Michael Watterson]

Frank Murphy wrote:
> Patrick O'Connor wrote:
>>
>>
>> On 01/07/07, *Frank Murphy* <frankly3d.weblists at gmail.com 
>> <mailto:frankly3d.weblists at gmail.com>> wrote:
>>
>>     Pre-Purchase Q?
>>
>>     Can I use a Hard Controller in a Soft-Raid box, basically as a
>>     means of
>>     attaching hds'?
>>     (Thinking Sata2)
>>
>>
>> As Niall said any sata/ide/scsi controller will do
>> I generally use cheapy non-raid pci sata controllers costing around 
>> €30/€40. I don't  see any point in using hardware controllers if 
>> using linux raid.
> Confused here,  How would the bios handle non-raid cards, or is it up 
> to the os (CentOS5) to pick them up?
> Maybe just don't know enough   always thought non-raid controllers had 
> to be irq 14\15 & as they are already in use?
>>
>>     If it then dies does a twin need to be installed, or will any do
>>
>> Not sure what you mean here??
> The controller-card Dying.
>>
>>     Frank
>>
>>     --
>>     http://www.frankly3d.com
>>     http://www.posermilitary.com
>>
>
>
HW raid works with multiple boot multiple OS
HW raid better performance, but only if it really is HW raid with it's 
OWN cpu and typically using some sort of SCSI. But SCSI expensive for disks.
Any PATA or SATA ide Raid I've seen seems to be really SW based. RAID 1 
(Mirror) in SW slows a system, RAID5 , while a higher CPU overhead may 
actually speed up a system if 4 drives are in the stripe set. I'm 
curious to try SATA, as PATA based IDE was always abysmal performance 
even compared to SW RAID 5 (which needed additional pair of disks as 
boot Mirror RAID 1).

Big advantage of HW RAID5 over SW RAID 5 is you can boot from it.

-- 
Michael Watterson
Senior Development Engineer
Digiweb Ltd.
IDA Business & Technology Park
Dundalk
Co. Louth
Ireland

www.digiweb.ie
+353 (0)42 9393 304