PERC 5/i question

William Warren hescominsoon at emmanuelcomputerconsulting.com
Tue Dec 12 06:59:56 CST 2006


IME with hardware raid you can move the disks between different cards of 
the same RAID level.  I have moved a 3 disk RAID 5 array between 
different controllers more than once without issue.

Ben Scott wrote:
> On 12/11/06, Matt Richardson <marichar at csusb.edu> wrote:
>> Is there an advantage to running software raid vs hardware raid?
> 
>   Software RAID is portable between hardware.  Hardware RAID is
> portable between software.
> 
>   In other words: Using Linux software RAID, you can move disks
> between controllers/machines/etc and still access the same disks.
> Using hardware RAID, you can boot two different OSes (or different
> versions of LVM, etc.) and still access the same disks.
> 
>   Hardware RAID can give you a performance benefit if your machine is
> busy running other tasks.  Software RAID can save you money if your
> CPU/RAM/bus/etc are lightly loaded and can spare the resources.
> 
>   In my experience, hardware RAID tends to be a bit more robust in the
> face of failures, but that might just be coincidence.
> 
>> Is it possible to configure a PERC 5/i (in a PE2950) to not act as a
>> raid controller?
> 
>   You can create a Logical Drive (LD) for each Physical Disk (PD) on
> the controller.  That effectively gives you one-to-one between LDs and
> PDs.  I'm not sure what overhead you'll incurr on the controller,
> though.  It might be you still pay the performance penalty of running
> through the RAID firmware and processor.
> 
>> This is all new to me as I used hardware raid on my
>> previous PEs, no lvm.  However, I like the flexibility lvm offers,
>> especially with xen guests.
> 
>   You can run LVM on top of hardware RAID.  LVM for storage
> management, hardware RAID for reliability.  I've done this before;
> works well.
> 
> -- Ben
> 
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every tongue that shall rise against thee in judgment thou shalt 
condemn. This is the heritage of the servants of the LORD, and their 
righteousness is of me, saith the LORD.

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