Log manager throughput considerations - No more than 3840K in-flight

Question

Hi Experts,
As per the documentation about Log Manager
Log manager throughput considerations
Outstanding log writes: 32-bit=Limit of 8, 64-bit=Limit of  32
No more than 3840K “in-flight”
Individual write size varies
Up to 60KB in size
in 64 Bit==> We can have 32 outstanding log writes and 1 log write size is max 60 KB so if there are 32 user dbs, max inflight  size can be 32*60KB==> 1920 KB. but documentation says 3840 KB
["No more than 3840K “in-flight"]. double the size of 1920 KB.
This is contradictory i think.
Manish

Answer 1

Thanks for the help.
http://blogs.msdn.com/b/sqlcat/archive/2013/09/10/diagnosing-transaction-log-performance-issues-and-limits-of-the-log-manager.aspx
Limits of the Log Manager
Within the SQL Server engine there are a couple limits related to the amount of I/O that can be "in-flight" at any given time; "in-flight" meaning log data for which the Log Manager has issued a write and not yet received an acknowledgement that the write has
completed. Once these limits are reached the Log Manager will wait for outstanding I/O’s to be acknowledged before issuing any more I/O to the log. These are hard limits and cannot be adjusted by a DBA. The limits imposed by the log manager are based on conscious
design decisions founded in providing a balance between data integrity and performance.
There are two specific limits, both of which are per database.
1. Amount of "outstanding log I/O" Limit.
a. SQL Server 2008: limit of 3840K at any given time
2. Amount of Outstanding I/O limit.
a. SQL Server 2005 SP1 or later (including SQL Server 2008 ):
i. 64-bit: Limit of 32 outstanding I/O’s
Regards
Manish