On Wed, Mar 13, 2013 at 4:08 PM, Arun Khan <knura9 at gmail.com> wrote: > 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. > Doubtful. The 6i are newer than the 5i. Months ago I tested and can confirm 5i cannot read 6i metadata (Dell and others are not lying). I've not tried swapping drives from a 5i into a 6i, then back to 5i to see if the 6i changed the metadata any. That's too much swapping for a hypothetical situation where an admin does not do a one-to-one swap (5i to 5i). > > > > Avoid SAS6/iR controllers ... they are low-end controllers that only > > support hardware RAID0 and RAID1. > And to add more information... the Dell PERC[56]i controllers are supported by the LSI SNMP daemon which then exports quite a bunch of information to SNMP. And that is useful with a Nagios plugin to keep tabs on array health. The SAS6/iR controllers are not compatible with that LSI SNMP daemon and so far I've not found a way to monitor their array health efficiently. The newest version of that Nagios script claims to support MPTFusion-based controllers (which the SAS6/iR is), but again I've not found a way to export the data to SNMP. [ OT: I confess...someone on this list pointed me at a Nagios plugin to check OpenManage that I've yet to test. :-/ ] > > 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 > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > -- ---~~.~~--- Mike // SilverTip257 //