Date: 5 Sep 2000 02:29:30 +0200 From: naddy@mips.inka.de (Christian Weisgerber) To: freebsd-scsi@freebsd.org Subject: Re: Keeping a DLT4000 streaming? Message-ID: <8p1epa$2vt5$1@ganerc.mips.inka.de> References: <8oth09$u2b$1@ganerc.mips.inka.de> <20000903154343.E564@freebie.demon.nl>
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Wilko Bulte <wkb@freebie.demon.nl> wrote: > DLTs need data like hungry piranhas to keep streaming ;-) I know. I'm prepared to shove as much down its throat as it will take, but somehow this fish doesn't want to swallow. > My DLT4000 generally does not stream. It is hooked up to a seperate > AH2940UW (you generally don't want your disks on the same SCSI > bus). Reportedly using tools like 'team' should help by buffering > the data. I have not tried that yet. I transfer single large files (complete filesystem dumps) from a holding disk to tape. The DLT4000 is on its own narrow/fast-10 bus (Sym810A), the disk is on a different wide/fast-20 bus (Sym875). Reading from the disk to /dev/null gives me ~8MB/s. I have used buffer(1) from the beginning, then tried team(1) as well. Tried different blocksizes, up to 64kB and multiples thereof. With compression _disabled_ the DLT streams along happily at 1.4MB/s, as shown by iostat(8). With compression _enabled_, it keeps backhitching. Average transfer rate, and in fact also the transfer rate for the short periods between stops when it is streaming, is ~2.7MB/s (as per "iostat -d 1"), give or take some, but under 3.0MB/s. > See the attached script to get compression and error stats from > the drive. I'll try this. > In addition there is a mode page setting (at least on DLT7000, > but I think 4000 has it too) that selects 'capacity' or 'speed' > mode. Details? The manual extensively documents the available mode page settings, and there is no mention of such an option. -- Christian "naddy" Weisgerber naddy@mips.inka.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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