You may have no problem with buffers >64k on Windows. It depends on the
SCSI drivers your hardware actually uses; we have some fibre channel
drivers that are fine up to large sizes. If it uses the Windows miniport
driver, then you do need to make registry changes. Search on the
internet for "MaximumSGlist". Here is an article that tells a good deal:
http://www.eetkorea.com/ARTICLES/2000APR/2000APR05_CT_ID_AN.PDF
You will have to find the registry key for your particular adapter. Here
is a bit for a Qlogic adapter:
6.1. System Registry Parameters
--------------------------------
* MaximumSGList
Windows includes enhanced scatter/gather list support for
doing very large SCSI I/O transfers. Windows supports up to
256 scatter/gather segments of 4096 bytes each, allowing transfers
up to 1048576 bytes.
NOTE: the OEMSETUP.INF file has been updated to automatically
update the registry to support 65 scatter/gather segments.
Normally, no additional changes will be necessary as this
typically results in the best overall performance.
If you wish to alter this value, please use the following
procedure:
1. Click on "Start", select "Run", and open the REGEDT32 program.
2. Select HKEY_LOCAL_MACHINE and follow the tree structure down to
the QLogic driver as follows:
HKEY_LOCAL_MACHINE
SYSTEM
CurrentControlSet
Services
Ql2300
Parameters
Device
3. Double click on
MaximumSGList:REG_DWORD:0x21
4. Enter a value from 16 to 255 (0x10 hex to 0xFF). A value of
255 (0xFF) enables the maximum 1 MByte transfer size. Setting
a value higher than 255 results with the default of 64K
transfers. The default value is 33 (0x21).
5. Click OK.
6. Exit the Registry Editor, then shutdown and reboot the system.
=====================
And another piece of the same info:
The formula to calculate the proper value for MaximumSGList is:
MaximumSGList = ((Maximum Block Size)/4 Kbytes) +1
For 256 Kbytes: 256 Kbytes/4 Kbytes = 64. Add 1 for 65 (decimal) or
0x41 (hexadecimal). The maximum value allowed for MaximumSGLIst is 255 or
0xFF. For the particular value of 0xFF, the internal value passed to
Windows
is increased to 0x101, allowing support for a full 1 Mbyte transfer.
The system must be rebooted for the new registry setting to be effective.
NOTE: For 64-bit systems, the OS page size is 8 Kbytes instead of 4
Kbytes.
Therefore, the maximum transfer size is 2 Mbytes, the default driver
installation enables support for 512 Kbytes transfer size, and the
formula becomes:
MaximumSGList = ((Maximum Block Size)/8 Kbytes) +1
William D L Brown
> You have a challenge here...I believe from a theoretical perspective
> this should work okay. However, if your solaris master was tuned
> with large buffers (>64K) then your new Windows 2K Master/Media
> server will not be able to read the data for restore. Unless you
> make some registry hacks (which I can't find now) on your W2K box.
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