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.
Greg
--
See complete headers for address and phone numbers
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message
