[CentOS] LSI/3ware 9750-4i and multipath I/O

John R Pierce pierce at hogranch.com
Fri Jan 13 19:37:11 UTC 2012

On 01/13/12 6:41 AM, Vahan Yerkanian wrote:
> multipath -ll showed everything OK, with both sdb and sdc (the same 24 x 3tb raid6 array) as active and ready.

are those controllers aware you're using them for multipathing?    RAID 
cards like that tend to have large caches, and one controllers cache 
won't see changes written to the other, leading to inconsistent data, 
unless the controllers have some form of back channel communications 
between them to coordinate their caches.

btw, thats _way_ too many disks in a single disk group, your disk 
rebuild times with 24 x raid6 will be ouch long. I try and limit my raid 
groups to 12 drives max, and stripe those.   given 24 disks, I'd 
probably have 2 hot spares, and 2 x 11 raid60, which would provide the 
space equivalent of 18 disks

john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast

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