Date: Tue, 10 Sep 2002 17:35:44 -0700 From: Kris Kennaway <kris@obsecurity.org> To: "Jack L. Stone" <jackstone@sage-one.net> Cc: freebsd-questions@freebsd.org Subject: Re: DD copy is too slow Message-ID: <20020911003544.GB77641@xor.obsecurity.org> In-Reply-To: <3.0.5.32.20020910183731.00fbeac8@mail.sage-one.net>
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[-- Attachment #1 --] On Tue, Sep 10, 2002 at 06:37:31PM -0500, Jack L. Stone wrote: > Am running FBSD 4.5-RELEASE > > On one of the servers, am having very slow real dd copy speed vs test and > don't know why. Below is the test first made that shows 25MB/s but the real > dd copy is only doing about half the speed. Other servers are matching the > test. Wonder what is wrong with this machine I/O....?? You've got double the disk I/O happening (read from ad0, write to ad1 _on the same IDE channel_). It won't be more than half the speed of a single-way transfer (and in fact is a bit less than half). You'll have better performance if you stick the drives on different channels or controllers. Kris [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (FreeBSD) iD8DBQE9fo/fWry0BWjoQKURAsrNAJ4vO7ZoEn7j/Jla5g2s2pnAP1gCPgCgplPy RtGT9QTFqUVTxQdzaj0jwjo= =iTMH -----END PGP SIGNATURE-----home | help
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