Date: Sat, 8 Apr 1995 22:02:50 +1000 From: Bruce Evans <bde@zeta.org.au> To: rgrimes@gndrsh.aac.dev.com, wilko@yedi.iaf.nl Cc: hackers@FreeBSD.org, smpatel@wam.umd.edu Subject: Re: large filesystems/multiple disks [RAID] Message-ID: <199504081202.WAA26434@godzilla.zeta.org.au>
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>> Ultrastore controllers have become famous for there in ability to do >> a decent job of getting data to and from the disk. >? As an owner of U24F card I'm interested in what is wrong with 'm? Is >grief and misery lurking somewhere ;-) ? They are slow. See my other mail that explains why they are no faster than IDE in important cases. This is despite their busmastering DMA at up to 66MB/sec compared with PIO at 3.3MB/sec. The DMA just reduces the transfer overhead and causes serial overruns. I suspect that there are performance bugs in the driver. What causes the maximum throughput to drop from 5MB/sec to 3MB/sec after /etc/rc is run? I suspect the controller or driver doesn't handle scatter/ gather right. Bruce
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