Messages in this thread | | | Date | Sun, 2 Nov 2003 21:34:30 -0800 (PST) | From | Andre Hedrick <> | Subject | Re: ide write cache issue? [Re: Something corrupts raid5 disks slightly during reboot] |
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On Sun, 2 Nov 2003, Ville Herva wrote:
> On Sat, Nov 01, 2003 at 10:05:31PM -0800, you [Andre Hedrick] wrote: > > > > I added the flush code to flush a drive in several places but it got > > pulled and munged. > > > > The original model was to flush each time a device was closed, when any > > partition mount point was released, and called by notifier. > > > > In a minimal partition count of 1, you had at least two flush before > > shutdown or reboot. > > > > So it was not the code because I fixed it, but then again I am retiring > > from formal maintainership. > > Thanks, Andre :(. > > As an^Wthe IDE expert, can you clarify a few points: > > - How long can the unwritten data linger in the drive cache if the drive > is otherwise idle? (Without an explicit flush and with write caching > enabled.)
Basically forever, until a read is issued to a range of lba's which starts smaller than the uncommitted contents's lba, and includes the content in question. Or if a flush cache or disable write-back cache is issued.
> I had unmounted the fs an raidstopped the md minutes before the boot.
The problem imho, is a break down of fundamental cascading callers.
Unmount MD -> flush MD
MD is a fakie device :-/
MD fakie calls for flush of R_DEV's
Likewise unloading or stopping MD operations should repeat regardless of mount or not.
> - Can this corruption happen on warmboot or only on poweroff?
Given POST (assume x86 for only a brief moment) will issue execute diagnositics to hunt for signatures on the ribbon, that basically wacks the content. Cool cycle obviously wacks the buffer.
> - What kind of corruption can one see the if boot takes place "too fast" > and drive hasn't got enough time to flush its cache?
erm, I am lost with the above. Flush Cache is a hold and wait on completion, period. However, a cache error at this point is a wasted effort to attempt recovery.
Not sure I helped or not ...
Cheers,
Andre
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