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 _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
