SUMMARY: Solaris 8 - UFS logging or logiing via DiskSuite Trans Metadevices

I share with you the response to questions that I asked Sun tech support
regarding filesystem logging.


Mike Box                       Phone: (540)231-9506
Systems Administrator            Fax: (540)231-3863
Department of Statistics      E-mail: Mike.Box@vt.edu
Virginia Tech

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>Can I implement UFS "logging" (via /etc/vfstab) on RAID5 and mirrored 
>filesystems without creating Trans Metadevices as described in 
>"Solstice DiskSuite 4.2.1 User's Guide" pages 91-99?  
>What are the pros and cons?

Yes you can enable UFS logging on raid5 and mirrored filesystem 
via solaris without creating transmetadevices.


UFS logging and Disksuite's trans metadevice logging serve the same
purpose which is
to store the UFS transactions in a log before the
transactions are applied to the file system.  However the two have
some differences as listed below:

a. The Disksuite logging is available with the Solstice Disksuite
   software while the UFS logging is part of the base OS from 
   Solaris 7.

b. The logging device to which the UFS transactions are initially
   stored is a separate metadevice object in Disksuite.  The log is
   allocated from free blocks on the same file system with UFS
   logging.

c. Since the logging device is a separate device with Disksuite, its
   size can be changed after configuration and also can be mirrored
   for additional reliability.  This is not possible with UFS logging
   as the logging device is part of the UFS filesystem.

d. A single logging device can be shared between trans metadevices
   with Disksuite.  The log is allocated for every individual UFS
   filesystem in case of UFS logging.

e. The UFS transactions can be flushed out of the log and
   written to the master file system using -f option of "lockfs" 
   command with UFSlogging.  This option is not available with 
   disksuite logging.



>Also, I mirrored / (root) partition which already had logging active.
>(Oversight) It seems to be working okay - no messages complaining otherwise.  
>Is this okay or have I "loaded a bullet in the chamber" of which I will
>become aware later at an inopportune time?


You can enable UFS logging on root NOT disksuite logging ( trans metadevices)
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