Block Writes Across Net May Cause Performance Hit (152348)
The information in this article applies to:
- Microsoft Windows NT Server 3.5
- Microsoft Windows NT Server 3.51
This article was previously published under Q152348 SYMPTOMS
When you are performing RAW mode writes using the redirector, you may incur
a performance hit from disk reads.
CAUSE
When the redirector sends a large block size across the net, it must divide
the blocks into chunks less than 64K to fit into a server message block
(SMB) packet. The redirector takes the size of the block and divides it by
the maximum data size (less than 64K) and uses this size to send the blocks
across the net. This result in an odd size being written to the disk on the
server side.
When the server receives the block to write (for example, 30K) it must then
write this information on page boundaries. On i386 and MIPS this is 4K, on
the DEC Alpha this is 8K. In the process of writing this data, it will be
forced to write information that is only part of a 4K or 8K page. In this
case is must read the portion of the page that has not changed, thus
causing the writes.
STATUS
Microsoft has confirmed this to be a problem in Windows NT version 3.51.
This problem was corrected in the latest Windows NT 3.51 U.S. Service
Pack. For information on obtaining the Service Pack, query on the
following word in the Microsoft Knowledge Base (without the spaces):
| Modification Type: | Major | Last Reviewed: | 11/4/2003 |
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| Keywords: | KB152348 |
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