Date: Thu, 2 May 1996 13:45:37 -0700 (MST) From: Don Yuniskis <dgy@rtd.com> To: wilko@yedi.iaf.nl (Wilko Bulte) Cc: freebsd-hackers@freefall.FreeBSD.org (FreeBSD hackers) Subject: Re: using DLT drive on FreeBSD Message-ID: <199605022045.NAA29327@seagull.rtd.com> In-Reply-To: <199605021801.UAA01622@yedi.iaf.nl> from "Wilko Bulte" at May 2, 96 08:01:19 pm
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> Hi there > > I 'found' myself a DEC TZ87 DLT drive destined for the scrapyard. This Hold onto it... I think the 2000 series is being discontinued... > is a 10/20Gb device (the 20Gb is using the optimistic 2:1 compression). > Quantum calls this a DLT2000. Apart from solving my backup needs for > the foreseeable future :-) I also have a few questions: Don't count on it! My 2500xt (15/30G) is already starting to max out when doing level 0 dumps.... :> Plus, the tapes are quite expensive and DON'T EVER DROP ONE! > First of all, the drive works just fine on my Asus P90/NCR810 > The main problem is that I cannot set the buffersize used by 'dump' > to a high enough value to keep the tape streaming. These puppies need > 1.3 - 2.5 Mbyte/second to keep streaming OK. The actual required rate is > dependent on how good the data compresses. An experiment @ work with a > Sun Sparc20 revealed a 1.9Mbyte/second transferrate while dumping the > /usr Solaris filesystem. Side note: I had to put the drive on a seperate > SCSIbus/adapter to make this work. I wouldn't even try to keep them streaming -- unless you've got a really fast disk subsystem *and* the DLT on a separate (FAST) SCSI adapter with nice short cables... > I think the 2.1R limit is 32kbytes. In the recent past there was a > discussion about this on this list (in relation to DAT drives??). Didn't > pay too much attention at the time because I did not have the drive then. > Is there any way to increase this value (seem to remember there was not.?) > > It is of course also possible that the HD & tape being on the same NCR810 > are hurting the streaming operation. Unfortunately, the you can't just issue a COPY command to the drive and give it the DLT as the destination!!! :> > NB looks like I also have to hack a bit into 'mt' to allow the density/ > compression settings to work. WIll dig up the device spec to see what > that has to say > > Comments? Look at amanda, too. --don
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