Path: utzoo!utgpu!jarvis.csri.toronto.edu!me!radio!helios!root
From: root@helios.toronto.edu (Operator)
Newsgroups: comp.os.vms
Subject: Re: What good are VMS RAMdisks anyway?
Message-ID: <549@helios.toronto.edu>
Date: 21 Apr 88 18:14:10 GMT
References: <8804180208.AA04234@ucbvax.Berkeley.EDU> <7544@ames.arpa>
Reply-To: sysruth@helios.physics.toronto.edu (Ruth Milner)
Organization: University of Toronto Physics/Astronomy Computing Consortium
Lines: 34

In article <7544@ames.arpa> pstevens@pioneer.UUCP (Paul Stevens RCE Sterling) writes:
> [...]
>
>Turbodisk does not save anything back to disk, so putting something
>like SYSUAF.DAT, though a high activity file, has the disadvantage of
>the possibility of losing data (like everyone's password change for the
>last N days since the RAM disk was installed :-( !)
>
Turbodisk *does* have a mechanism for saving things back to disk - *if*
you tell it to do so. Using it, however, brings in the issue of "at what
point does saving things back to disk cancel out the performance improve-
ments gained by having it in the first place?". You can tell TurboDisk
to BACKUP the contents of the RAM disk (back to the original files?) at
a fixed, manager-adjustable, frequency (e.g. every 10 minutes, every hour,
every 24 hours, etc.). Since I only tested the free demo, I don't recall
whether you can specify certain files which should be written out, or if
it always does the whole thing. If the latter, and it's a large chunk of
memory, you probably don't want to do it very often. But it can be done,
at least as a BACKUP saveset. So if the system crashed you would only
lose the changes made since the last copy operation.

However, TurboDisk is really designed to hold files which are read a lot,
so I don't think it would help to put high-write-activity files on it.

>Paul Stevens - NASA Ames Research Center Moffet Field CA
>               Mail Stop 233-10
>               (415)694-4887
>	       pstevens@ames-pioneer.arpa

-- 
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