On Tuesday, 11 December 2001 at 15:34:37 +0100, Wilko Bulte wrote:
> On Tue, Dec 11, 2001 at 11:06:33AM +1030, Greg Lehey wrote:
>> On Monday, 10 December 2001 at 10:30:04 -0800, Matthew Dillon wrote:
>>>>>     performance without it - for reading OR writing.  It doesn't matter
>>>>>     so much for RAID{1,10},  but it matters a whole lot for something like
>>>>>     RAID-5 where the difference between a spindle-synced read or write
>>>>>     and a non-spindle-synched read or write can be upwards of 35%.
>>>> If you have RAID5 with I/O sizes that result in full-stripe operations.
>>>     Well, 'more then one disk' operations anyway, for random-I/O.  Caching
>>>     takes care of sequential I/O reasonably well but random-I/O goes down
>>>     the drain for writes if you aren't spindle synced, no matter what
>>>     the stripe size,
>> Can you explain this?  I don't see it.  In FreeBSD, just about all I/O
>> goes to buffer cache.
>>>     and will go down the drain for reads if you cross a stripe -
>>>     something that is quite common I think.
>> I think this is what Mike was referring to when talking about parity
>> calculation.  In any case, going across a stripe boundary is not a
>> good idea, though of course it can't be avoided.  That's one of the
>> arguments for large stripes.
> In a former life I was involved with a HB striping product for SysVr2
> that had a slightly modified filesystem that 'knew' when it was
> working on a striped disk. And as it know, it avoided posting I/O s
> that crossed stripes.

So what did it do with user requests which crossed stripes?

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