Microsoft KB Archive/894722

= You experience slower performance in Server for NFS when you use a software-based RAID system together with Windows Storage Server 2003 =

Article ID: 894722

Article Last Modified on 3/8/2005

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APPLIES TO


 * Microsoft Windows Storage Server 2003
 * Microsoft Windows Services for Unix 2.2
 * Microsoft Windows Services for Unix 2.3

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SYMPTOMS
You experience slower performance in Server for NFS when you use a software-based RAID system together with Microsoft Windows Storage Server 2003. When WRITE operations are performed from a Network File System (NFS) client to an NFS server, you experience the following symptom:

The transfer of files to a Microsoft Windows 2000-based NFS server that is running Microsoft Windows Services for UNIX 2.3 or Windows Services for UNIX 2.2 is faster than the transfer of files to an NFS server that is running Server for NFS together with Windows Storage Server 2003.



CAUSE
This issue occurs because Server for NFS handles caching differently in Windows Storage Server 2003 than how Server for NFS handles caching in Microsoft Windows Powered Network Attached Storage (NAS) 2.x. Therefore, you may experience decreased performance in WRITE operations to a computer that is running Server for NFS together with Windows Storage Server 2003.

The Server for NFS program in Windows Storage Server 2003 does not perform write caching on the system cache. Instead, Server for NFS in Windows Storage Server 2003 always writes data directly to the hard disk. Therefore, in a software-based RAID scenario, you may experience decreased performance if you compare NFS WRITE operations between Windows Storage Server 2003 and Windows Powered NAS 2.x.

Additionally, you may notice slower performance when a computer that is running the Windows Services for UNIX 3.5 Client for NFS program performs WRITE operations to the NFS server than when other NFS client programs perform WRITE operations to the same NFS server. This issue occurs because the Services for UNIX 3.5 Client for NFS performs synchronous WRITE operations to the NFS server. Therefore, the Client for NFS program waits for the first WRITE operation to complete before the Client for NFS performs a second WRITE operation. Other NFS client programs, such as the Linux NFS client program, are configured to have multiple asynchronous WRITE requests.



WORKAROUND
If you have a hard disk controller that has a configurable write cache, enable this cache.

Important If your hard disk controller does not have a backup battery, you may experience data loss or data corruption when you enable write caching. Data loss or data corruption may occur if your computer unexpectedly loses power. Therefore, we recommend that you see your computer documentation or that you contact your hardware vendor to determine whether your hard disk controller has an appropriate backup battery. Alternatively, you can connect a UPS to your computer.

For information about how to contact computer hardware vendors, click the appropriate article number in the following list to view the article in the Microsoft Knowledge Base:

65416 Hardware and software vendor contact information, A-K

60781 Hardware and software vendor contact information, L-P

60782 Hardware and software vendor contact information, Q-Z



MORE INFORMATION
The implementation of the Cache Manager component in Windows Storage Server 2003 differs from Windows Powered NAS 2.x. Server for NFS 3.0 that is included with Network Attached Storage 3.0 no longer relies on Cache Manager to cache WRITE operations. Instead, Server for NFS always writes data directly to the hard disk. This change causes write performance in Server for NFS to be slower than write performance in Windows Services for UNIX 2.3 or Windows Services for UNIX 2.2. Because Server for NFS in Windows Storage Server 2003 always writes data directly to the hard disk, Server for NFS in Windows Storage Server 2003 no longer relies on the following registry value to control caching:

Value name: UseWriteCache

Value type: REG_DWORD

Instead, caching behavior is controlled by client protocol requests when those clients mount NFS shares.

Additional query words: SFU 3.0 write through Interix NAS SAK

Keywords: kbtshoot KB894722

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