[CentOS] [OT/HW] hardware raid -- comment/experience with 3Ware

[Arun Khan]

On Wed, Mar 13, 2013 at 6:37 PM, SilverTip257  wrote:
> On Tue, Mar 12, 2013 at 10:10 PM, Keith Keller wrote:
>
>> On 2013-03-12, SilverTip257 <silvertip257 at gmail.com> wrote:
>> >
>> > I've not had any MegaRAID controllers fail, so I can only say they've
>> been
>> > reliable thus far!
>>
>> I think that this is not a helpful comment for the OP.  He wants to
>> know, in the event the controller does fail, can he replace it with a
>> similar-but-possibly-not-identical controller and have it recognize the
>>
>
> I've had no problem with various versions of Dell MegaRAID/PERC5i
> controllers.
> You can swap drives from a PERC5i into a PERC6i for example and things are
> peachy.  But it is not possible to swap drives from a PERC6i into a PERC5i
> controller.
>

No plans to go with Dell hardware but it is great to note that newer
models (Dell OEM Megaraid) recognize arrays created with older models.
 I don't expect an older model to recognize an array created by a
newer model.


> Avoid SAS6/iR controllers ... they are low-end controllers that only
> support hardware RAID0 and RAID1.

My configuration will be RAID 5 or 6, depending on how the option the
client is willing to pay.

>
> Ultimately hardware RAID controllers can be a big pain -- just like
> anything else it's a good business practice to have spares!
>
>
>> original RAID containers.  Just because you have not seen any failures
>> so far does not mean the OP never will.
>>
>> > You start by failing/removing the drive via mdadm.  Then hot remove the
>> > disk from the subsystem (ex: SCSI [0]) and finally physically remove it.
>> >  Then work in the opposite direction ... hot add (SCSI [1]), clone the
>> > partition layout from one drive to the new with sfdisk, and finally add
>> the
>> > new disk/partitions to your softraid array with mdadm.
>> >
>> > You must hot remove the disk from the SCSI subsystem or the block device
>> > (ex: /dev/sdc) name is occupied and unavailable for the new disk you put
>> in
>> > the system.  I've used the above procedure many times to repair softraid
>> > arrays while keeping systems online.
>>
>> This is basically the same procedure for replacing a failed drive in a
>> hardware RAID array, except that there is no need to worry about drive
>>
>
> I'll argue that the software RAID process is slightly more complex.  And it
> is crucial that one remember to hot-remove the disk ... after all one
> could panic their box by just yanking the drive.
>

Yes, this could happen inspite of well documented procedures.  For
this reason, hardware RAID has been a consideration.  However, I have
come to realize that  it has it's own pros and cons as mentioned in
this thread.

-- Arun Khan