On Tue, Mar 12, 2013 at 4:30 AM, Arun Khan knura9@gmail.com wrote:
On Thu, Mar 7, 2013 at 12:07 AM, Gordon Messmer wrote:
On 03/06/2013 08:35 AM, Arun Khan wrote:
Any preference between 1 and 2 above.
Based on about 10 years of running a hundred or so systems with 3ware controllers, I would say that you're better off with an LSI MegaRAID card, or with Linux software RAID. 3ware cards themselves have been the most problematic component of any system I've run in my entire professional career (starting in 1996). Even very recent cards fail in a wide variety of ways, and there is no guarantee that if your array fails using a controller that you buy now that you'll be able to connect it to a controller that you buy later.
@ Gordon - thanks for sharing this piece of info! In case of RAID card failure, it is important to be able to recover the data (RAID device) with a compatible replacement. Are the LSI MegaRAID controller more reliable in this respect?
I've not had any MegaRAID controllers fail, so I can only say they've been reliable thus far!
At this point, I deploy almost exclusively systems running Linux with KVM on top of software RAID. While I lose the battery backed write cache (which is great for performance unless you sustain enough writes to fill it completely, at which point the system grinds nearly to a halt), I gain a consistent set of management tools and the ability to move a disk array to any hardware that accepts the same form factor disk. The reliability of my systems has improved significantly since I moved to software RAID.
Software RAID is an option but I don't think hot swap is possible without some tinkering with the mdadm tool a priori.
Hot swap really depends on what your HBA or RAID controller supports.
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.
[0] https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/5/ht... [1] https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/5/ht...
The systems will go to client site (remote), prefer to keep the
support calls to remove/replace hardware activity :(
Thanks, -- Arun Khan _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos