Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!munnari.oz.au!metro!cluster!yar
From: yar@cs.su.oz (Ray Loyzaga)
Newsgroups: comp.unix.large
Subject: Re: tape/backup systems
Message-ID: <1190@cluster.cs.su.oz.au>
Date: 11 Sep 90 02:58:16 GMT
References: <12701@encore.Encore.COM>
Sender: news@cluster.cs.su.oz.au
Reply-To: yar@cluster.cs.su.oz (Ray Loyzaga)
Organization: Basser Dept of Computer Science, University of Sydney, Australia
Lines: 53

In article <12701@encore.Encore.COM> terryk@encore.com (Terence Kelleher) writes:
> How do large systems typically deal with the problem of backups?  I am
> trying to find answers for a 50-100 Gbyte disk system.  
> 
> Although 8mm and 4mm have the capacity to handle the amount of data
> efficiently, the transfer rates are quite slow, given the volume of
> data to move.  Also, the reliability of the heilical scan devices is
> well established.
> 
> 9-track tapes have the speed to handle the volume, but the number of
> tapes required and the need to change tapes so often make storage and
> operator involvement big issues.
> 
> What other solutions exist for Unix systems?
> -- 
> Terence Kelleher
> Encore Computer Corporation
> terryk@encore.com

Talk to Sony and HP about WORM and magneto-optical disk systems.
There is also an interesting system incorporated in the Plan-9
filesystem, the filesystem is implemented on a very large WORM
(120Gb?), and disk/memory is a cache for it. You get a copy on
write version of a file, which will eventually get onto the WORM.

The larger optical jukeboxes will let you do unattended backups,
but the disks are rather expensive. We will be getting a
20Gb "write many" jukebox which will be used for unattended backups
and for an archival/retrieval system.
The system will allow for online retrieval of quite recent material
and when the jukebox is nearly full, the older platters can be
stored away, much like tapes.
The biggest reason why we are going this way is that most users
are using disk to store data that they would be perfectly happy
to put on a reliable system that will return the data in a timely
fashion, they don't look at some files for years, but it gives
them a cosy feeling to keep them around. If they could get them
back from an archival system in a few minutes they won't need to
keep in on our fast and expensive hard disks. These systems
also have benefit for program/system development because it becomes
a trivial matter to store a snapshot of a system under development
without running into disk space limits. E.g. its nice to keep
a copy of X11.3 around but it doesn't have to be on disk, and
tape is too slow, so in a few tens of seconds you can access it on
a jukebox system.
My guess is that a lot of work will be going into these sorts
of storage systems in the future.

It is fast reaching the point in our department where we have
more disk than we can comfortably manage and the growth in usage
is being driven by the fact that we have given up trying.
Nobody knows what they are keeping in their directories just
in case they need it in the future.