Date: Mon, 6 Jan 1997 10:34:35 -0500 (EST) From: John Dowdal <jdowdal@destiny.erols.com> To: Andre Albsmeier <Andre.Albsmeier@mchp.siemens.de> Cc: freebsd-scsi@freebsd.org Subject: Re: put SCSI disk on same controller as DLT or not? Message-ID: <Pine.BSI.3.95.970106102214.3125A-100000@destiny.erols.com> In-Reply-To: <199701061322.OAA14038@server.us.tld>
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On Mon, 6 Jan 1997, Andre Albsmeier wrote:
> Hi,
>
> don't know if this belongs to -scsi or -hardware or elswhere...
>
> I'm running 2.2-BETA on a P166 with two Adaptec 2940. I plan to use
> amanda to do backups on a DEC DLT which is connected to one of the
> two 2940s. Since a lot of files to be backed up come via a 10 MBps network, I
> want to use a holding disk where the data is being collcted first and then
> written to the DLT (which is significantly faster than the network).
>
> To optimize performance, I would like to know if I should connect the holding
> disk to the same 2940 as the DLT is attached to or to the other one.
>
> My thoughts are, that if I had both devices on different controllers, the
> throughput could be faster since the data is read from one controller
> and pushed directly to the other one.
>
> Maybe someone has already experience with this, or some of the SCSI experts
> can give me a small hint...
I used to work for the comp sci department at university of maryland
[where amanda was written], where they have a couple hundred machines
backed up to a 20GB DLT tape on an old DEC 3000 (alpha). The DLT [with
compression disabled; using gzip on clients] was able to stream 1500KB/s,
The holding disk was an 9GB seagate elite [5400 RPM].
When the dumps were coming in over the network, the tape did not stream
[got about 1/2 the maximum throughput] because the holding disk was
thrashing from 10 other dumps coming in from other machines at the same
time. When the holding disk was otherwise idle, the system streamed the
tape.
The amanda server had a single Turbochannel [DEC bus] 10mbit scsi
controller and 6 devices, but I don't think the machine would have
performed much better with two scsi controllers since the disk was seeking
itself to death most of the amanda run.
There exists a "amanda-users@cs.umd.edu" mailing list for amanda specific
questions. To subscribe (stolen from amanda readme)
amanda-users
The amanda-users mailing list is for questions and general discussion
about the Amanda Network Backup Manager. This package and related
files are available via anonymous FTP from ftp.cs.umd.edu in the
pub/amanda directory. NOTE: the amanda-users list is itself on the
amanda-announce distribution, so you only need to subscribe to one of
the two lists, not both.
To subscribe, send a message to amanda-users-request@cs.umd.edu.
John
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