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Using mapped drives or NAS drives for remote data access

Article Number: 2008
First Published:
Modified:
Recent Activity:
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OS: Windows, Unix, OpenVMS
Product: Operating System, xfServer

Synergex does not recommend using network shares (mapped drives) or NAS (network-attached storage) drives (such as NFS and SMB/CIFS or Samba) for accessing remote Synergy data, and we provide only very limited support for this configuration.


Our experience, and that of our customers, has shown that mapped and NAS drives are not reliable. They are known to cause data corruption and locking failures, as well as performance issues, and the instances of these issues seem to be increasing as customers upgrade to new versions of Windows. Instead of mapped drives, we recommend Synergy/DE xfServer or Microsoft’s Windows Terminal Services (so that the data files are local to the dbr process). With xfServer, when a network connection is lost, it properly closes files. This is not the case with a mapped drive, where the loss of a network connection during file I/O will likely result in corruption. Instead of NAS drives, we recommend SAN (storage area network or "native") drives.


File corruption issues aside, in most cases xfServer will significantly outperform a mapped drive in commercial situations with multi-user access when it’s set up to correctly use SCSCOMPR and SCSPREFETCH in conjunction with correctly opening files for input when just reading data sequentially. The known cases where xfServer is slower than a mapped drive is when a file is opened for update with a single user or exclusive access, or for output when the file is not large and/or the records are small (or ISAM compression makes them small), allowing the redirector to cache the data blocks locally. If oplocks are turned off on Windows server systems, this caching is disabled and performance degrades, though reliability increases.


Synergy/DE Developer Support will try to assist you if you encounter issues while using mapped or NAS drives, but their ability to help will be limited. We may require you to reproduce your issues using a demo copy of Synergy/DE xfServer before we can diagnose the problem. Also, we can help recover corrupt files, but we may not be able to help figure out the specific causes of the corruption.


If you choose to use mapped drives or NAS drives, we recommend you do the following;

  1. Make sure you have all the latest updates. For mapped drives, get those related to srv.sys, rdbss.sysmrxsmb10.sys, and mrxsmb20.sys. For Samba (SMB/CIFS), get the latest Samba server updates.
  2. Make sure you are using Synergy/DE’s isutl utility on a regular basis to verify the integrity of your files. You can set up an automated process to do this. Isutl can also identify areas where performance can be improved.


If you have any questions or would like more information about this topic, please contact Synergy/DE Developer Support or your account manager.



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