Date: Wed, 22 Mar 1995 22:04:50 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, hasty@star-gate.com Cc: hackers@FreeBSD.org Subject: Re: Why IDE is bad Message-ID: <199503221204.WAA12708@godzilla.zeta.org.au>
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>>`cp -pR /usr/src/sys /usr/src/sys~' takes 85 seconds to copy >>2 * 12475K (293K/sec). Any IDE drive can compete with this transfer >>rate. >Now why during a normal transfer is scsi so slow? >Is it because of the updates to the inodes? I think it's partly for synchronous updates and partly for small i/o's. The bt445c-xp34301 runs at about half its maximum speed for 8K blocks, 1/4 of its maximum speed for 4K blocks, down to 1/20 of its maximum speed (about 293K/sec :-) for 512-byte blocks. This is for sequential input. Reading the same 512-byte block over and over is no faster. The AdaptecVLB with a P2100 (?) is reported to be about the same speed. The U34F is almost twice as slow. IDE is faster for small i/o's. Bruce
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