[CentOS] reboot - is there a timeout on filesystem flush?

Wed Jan 7 20:08:54 UTC 2015
John R Pierce <pierce at hogranch.com>

On 1/7/2015 11:30 AM, Gary Greene wrote:
> During the reboot, most card’s drivers on init, will invalidate the cache on the card to ensure dirty pages of data don’t get flushed to disk, to prevent scribbling junk data to the platters. From what I recall, this is true of both the megaraid and adaptec based cards.

Presumably, this cache invalidation is only on cards that don't have 
battery (or flash) backed write cache?     Doing that on a BB/FBWC 
system would negate the usefulness of said battery backed cache entirely.

IMHO, an even bigger problem is using cheap desktop class SATA drives 
for server storage.    These FREQUENTLY lie about write commits.    This 
sort of behavior is a VERY good reason to stick with vendor qualified 
and branded server drives that have been tested to work with the 
specific controller + backplane configurations they are sold with.   And 
yes, those drives cost 2-3X more than your Newegg/Amazon elcheapo 
desktop stuff.

All of this controller and drive behavior is a VERY good argument for 
the use of end to end checksumming like ZFS does...  a ZFS 'scrub' 
operation WILL detect any data corruption on the file system and raid, 
whatever the source, and many inconsistencies can be corrected, such as 
one disk of a mirror having a stale block.

john r pierce                                      37N 122W
somewhere on the middle of the left coast