When the Maxtransfersizeis set in xp_backup_database, the I/Os going to the backup media (disk) are 1MB in size. The READ I/Os on the source disk are correct.
During the SQL Server Backup when the Maxtransfersize is set to 64 KB, the write I/Os are also 64 KB in size.
Example: MaxTransferSize of 64KB
SQL Litespeed:
Read I/O Size: 64 KB
Write I/O Size: 1MB
Native SQL Backup:
Read I/O Size: 64 KB
Write I/O Size: 64 KB
How to change the write I/O size?
WORKAROUND:
exec master.dbo.xp_backup_database
@database = N'DailyDB',
@backupname = N'DailyDB - Full Database Backup',
@desc = N'Full Backup of DailyDB on 7/13/2012 9:47:21 AM',
@compressionlevel = 2,
@filename = N'C:\BACKUP\DailyDB_201207130947.bak',
@init = 1,
@with = N'STATS = 10',
@BaseSize = 524288
GO
BaseSize is The smallest chunk of memory LiteSpeed attempts to write to disk at any given time.
