On Jul 28, 2009, at 6:34 PM, Eric D. Mudama wrote:
On Mon, Jul 27 at 13:50, Richard Elling wrote:
On Jul 27, 2009, at 10:27 AM, Eric D. Mudama wrote:
Can *someone* please name a single drive+firmware or RAID
controller+firmware that ignores FLUSH CACHE / FLUSH CACHE EXT
commands? Or worse, responds "ok" when the flush hasn't occurred?
two seconds with google shows
http://seagate.custkb.com/seagate/crm/selfservice/search.jsp?DocId=183771&NewLang=en&Hilite=cache+flush
Give it up. These things happen. Not much you can do about it, other
than design around it.
-- richard
That example is a windows-specific, and is a software driver, where
the data integrity feature must be manually disabled by the end user.
The default behavior was always maximum data protection.
I don't think you read the post. It specifically says, "Previous
versions
of the Promise drivers ignored the flush cache command until system
power down. " Promise makes RAID controllers and has a firmware
fix for this. This is the kind of thing we face: some performance
engineer tries to get an edge by assuming there is only one case
where cache flush matters.
Another 2 seconds with google shows:
http://sunsolve.sun.com/search/document.do?assetkey=1-66-200007-1
(interestingly, for this one, fsck also fails)
http://sunsolve.sun.com/search/document.do?assetkey=1-21-103622-06-1
http://forums.seagate.com/stx/board/message?board.id=freeagent&message.id=5060&query.id=3999#M5060
But they also get cache flush code wrong in the opposite direction. A
good example of that is the notorious Seagate 1.5 TB disk "stutter"
problem.
NB, for the most part, vendors do not air their dirty laundry (eg bug
reports)
on the internet for those without support contracts. If you have a
support
contract, your search may show many more cases.
While perhaps analagous at some level, the perpetual "your hardware
must be crappy/cheap/not-as-expensive-as-mine" doesn't seem to be a
sufficient explanation when things go wrong, like complete loss of a
pool.
As I said before, it is a systems engineering problem. If you do your
own systems engineering, then you should make sure the components
you select work as you expect.
-- richard
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