I concur with Ingo. Let us get started, we are already in November, leaving me very little time for implementation...
A1 can be seamlessly be implemented by backup kernel in the future, if the initial current bytes are not enough. The backup system beneath BSM will most likely have to store out-of-band meta-info anyway, with perhaps the exception of the default file BSM (perhaps solvable with use of table in system database/information schema etc, haven't analyzed all the possibilities yet).
A3 is, I feel, is like being stuck between a rock and a hard place... Code must be added for async I/O. The buffer sent from storage engine must be processed and used in chunks if it can't be written in whole. On the other hand; if the BSM report a preferred buffer size smaller than storage engine deliver, we still have to implement the code. Sooooo, A3 will be implemented regardless, but not because of an async I/O need.
Also note; Most backup systems are slow, meaning that we can expect anything from milliseconds to days, before the data can actually be written. This has to do with the resource allocation within the backup system. I intend to implement a timeout watchdog thread, which will abort waiting I/O operations, and thus abort the backup. Usual default value is 300 seconds. A timeout variable should be implemented for the BSM as well. This approach is de facto standard and quite common in the backup world.
Best regards / Cordialement
From: Ingo.Struewing@stripped [mailto:Ingo.Struewing@Sun.COM]
Sent: 4. november 2009 15:21
To: Rafal Somla
Cc: Lars Thalmann; Rafal Somla; Andreas Almroth; email@example.com
Subject: Re: HLS approved: WL#5046 - Online Backup: Pluggable Storage Modules
Rafal Somla, 04.11.2009 13:58:
> I assume you won't object if after all we decide to go
> with alternatives A1 and A3.
Yesterday I got the impression that the discussion got stuck. I found it
was time to make a decision. I decided to accept the HLS as is, with the
alternatives as discarded ideas.
Please respect my decision. Please don't restart the discussion. Let us
go ahead with the LLD.
Ingo Strüwing, Database Group
Sun Microsystems GmbH, Sonnenallee 1, D-85551 Kirchheim-Heimstetten
Geschäftsführer: Thomas Schröder, Wolfgang Engels, Wolf Frenkel
Vorsitzender des Aufsichtsrates: Martin Häring HRB München 161028