Yogesh Pahilwan wrote:

Where can we get documentation (design/implementation) about RAID6 and
bitmap for linux kernel 2.6.

For the bitmap code, I'm afraid you'll just have to read the code. Also, 
look back at the archives of this list. There are several discussions 
about the bitmap patches, going back to 2003.

--
Paul

-----Original Message-----
From: Paul Clements [mailto:paul.clements@steeleye.com] 
Sent: Wednesday, March 22, 2006 11:37 PM
To: Yogesh Pahilwan
Cc: 'Neil Brown'; linux-raid@vger.kernel.org
Subject: Re: Linux MD RAID5/6 bitmap patches

Yogesh Pahilwan wrote:

quoted

Thanks for your reply. As far as what I understood that when we apply the
bitmap patch, for every write it will do 2 sync writes that is setting the
dirty bit, writing intent log and one async write for clearing the dirty
bit. Is it correct?

The bits are in the intent log, so the "setting dirty bit" and "writing 
intent log" are the same thing. Just one write.

quoted

If that is the case are there any patches available which can do

collection

quoted

of sync write in a queue and write a collection in single write request.
For Eg:
For 10 writes , we will have 10 + 1 sync writes + 10 async write.

The bitmap code already does this by default. The bitmap writes are 
queued up so that all writes to a given page (within a short time 
period) are reduced to a single write. The performance is actually quite 
good. There's very little performance difference between having a bitmap 
versus not having one.

quoted

I mean to say , 10 sync writes for setting the dirty bits + 1 sync write

for

quoted

write intent log for all queued request in one write operation + 10 async
write for clearing the dirty bit.

The async writes for clearing the bitmap are also combined.

--
Paul

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