Hello Cephers,
I got some questions regarding where what type of IO is generated.
As far as I understand it looks like this (please see picture: http://imageshack.com/a/img673/4563/zctaGA.jpg ) :
1. Clients -> OSD (Journal):
- Is it sequential write?
- Is it parallel due to the many open sockets?
2. OSD journal flush -> Filestore:
- Is it periodic sequential write?
- Is it done in parallel to the Filestore or just with one writer?
3. OSD -> Clients:
- Is it parallel random read (due to distribution of objects to PGs over many OSD's)?
- Is any reading (from client side) done from journals?
How is the writing to the journal done? Is it like a ringbuffer - every new block is added to the end of the journal so that there is no "overwriting" in the middle of the journal (that would force the head of the HDD (if not SSD) to seek?
It would be nice if you would correct me if anything is wrong here.
Thanks in advance,
Steffen
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