ADSM-L

Re: ADSM-Server on Sun Sever

1999-08-05 09:52:12
Subject: Re: ADSM-Server on Sun Sever
From: Richard Sims <rbs AT BU DOT EDU>
Date: Thu, 5 Aug 1999 09:52:12 -0400
>What version of ADSM are you on?  The reason the format takes so long is
>that the format process is calling sync every N number of writes.  I had
>some trouble with my DB, and Sun Server Development sent me a dsmserv
>module that did not do the sync calls, and I formated my 5GB recovery log
>in 15 minutes, rather than 6 hours.  Since 15 minutes is not much time to
>waste if the system crashed during the process (no call to sync), it
>doesn't make much sense to protect this operation (with periodic sync
>calls).  Just call it once at the end (which close probably does anyway).
>
>I dunno if the sync calls have been removed by now (3.1.2.40), but perhaps
>the Sun Developers listening here could comment.

Steve - That's very informative.  I doubt that the syncing has been removed
        in that dsmserv is a general module and needs to assure that its
ordinary work gets saved to disk regularly.

An idea immediately came to mind, though...  The dsmserv module has
historically been unstripped, presenting the opportunity of preparing a
special copy for restorals and the like with the fsync CSECT replaced with a
dummy function which simply returns, by statically linking that function into
the module so that it won't be taken from a shared library.  This will, as you
say, provide great gains in performance for these non-online tasks.  Remember,
too, that Unix systems themselves perform periodic syncing through syncd or
other facility.

   Richard Sims, BU
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