As I’ve read and understood; it isn’t due to actual functionality though. It is 
as you say, due mostly to longer rebuild times (indexing a physically larger 
geometry than the rest of the array members, for a smaller logical geometry) 
and the risk (rare IMO) to the rest of the array (as a rebuild will stress the 
array and could cause other, near-death disks to fail thereby causing the array 
to fail). It also wastes the extra horsepower of the disk since the existing 
RAID can’t capitalize on the resources of the larger disk.

So in a case of, would you go out and buy a new disk that way .... I’d say no; 
but if that is the result of a covered RMA, I’d say go for it.

I’m no diskologist though ... just based on my own experiences of what has 
worked for me for the last couple of decades ... and I’ve never lost a server 
... outside of that one time when my pants pocket snagged the release on the 
2nd disk in a R5 on my way out the door ... bad memories.

-Ryan

On Nov 14, 2017, at 9:03 AM, Charles Goldsmith 
<[email protected]<mailto:[email protected]>> wrote:

Keep in mind, RAID 5 is ok for smaller disks, but larger disks it's no longer 
recommended, but sadly, the best article about it is from Dell: 
http://en.community.dell.com/techcenter/b/techcenter/archive/2012/08/14/new-equallogic-raid-tech-report-considerations-and-best-practices-released

With bigger disks, it's even said that RAID 6 is no longer good enough, due to 
large rebuild times in case of a failure.  
http://www.zdnet.com/blog/storage/why-raid-6-stops-working-in-2019/805

On Tue, Nov 14, 2017 at 7:41 AM, Ryan Huff 
<[email protected]<mailto:[email protected]>> wrote:
Reto,

Seek/rpm speeds and media type (flash, sata ... etc) are usually what matter 
the most for RAID disks. If your only difference is total storage capacity, the 
bigger disk will usually work just fine, your just gonna waste the additional 
154GB of space (because the RAID will only provision 146GB of that 300GB disk).

Just remember on a RAID 5, don’t pull/lose more that 1 disk at a time .... 
painful lesson long ago I share over beer every now and then.

-Ryan

On Nov 14, 2017, at 8:23 AM, Reto Gassmann <[email protected]<mailto:[email protected]>> 
wrote:

Hallo

We have a UCS C210 Server with 10x146 GB Disks. One of the Disks failed and I 
got a 300 GB replacement Disk from Cisco.

Is that a problem if I replace the defect 146 Disk in the RAID 5 with a 300 GB 
Disk?

Thanks for help
Regards Reto
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