On Wed, Nov 14, 2012 at 12:37 PM, Stephen John Smoogen <[log in to unmask]> wrote:
> On 14 November 2012 10:20, Ken Teh <[log in to unmask]> wrote:
>> The common thread is I/O to a MegaRAID raid5 device.  Which is cause for
>> concern since the primary function of both machines where I've encountered
>> this problem is file-serving.
>>
>> Perhaps I am just unlucky and have 2 bad MegaRAID cards in a row.  I'm
>> trying
>> to understand this better, figure out if I am doing something wrong.
>
> Well there are a couple of issues this could be:
>
> 1) You are asking more than the MegaRaid is meant to do... it may be
> running out of cache, or other resources.

My experience with MegaRAID has been *horrible*. Poor driver
compatibility, awkward and destructive firmware, and deceitful
specifications only start the list of horrible failures. Their best
technological use is as doorstops.

> 2) The megaraid is still rebuilding its array beneath and you are
> hitting a locking problem because it hasn't finished what it needs to
> do before you ask it to do something else (really sort of #1).
>
> Most of the time you will need to install the proprietary Megaraid
> tools to see what is going on under the disks to find out.

See above: good luck getting those tools working!

Every hour you spend waiting on those things to come to their senses,
or trying to debug them, is an hour wasted on problems that may not
ever be solved by your efforts. I encourage you to replace them with a
better quality manufacturer: Adaptec makes very solid, not too
expensive controllers, and Rocketport remains the cream of the crop.