Date: Wed, 4 Jun 1997 03:37:06 +1000 From: Bruce Evans <bde@zeta.org.au> To: gibbs@plutotech.com, luigi@labinfo.iet.unipi.it Cc: hackers@FreeBSD.ORG, toor@dyson.iquest.net Subject: Re: disk scheduling (was Re: DMA for IDE drives ?) Message-ID: <199706031737.DAA24220@godzilla.zeta.org.au>
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>My QUANTUM FIREBALL_TM3200S 300X with a 2940A Ultra SCSI does a >mere 3MB/s writing (iozone 64 8192), on a PPRO-200. Not impressive, >considering a WDC AC21600H does 4.9MB/s on the same hardware (in >both cases, a P5-133 gives almost the same results, it is not >cpu-limited). The WDC AC21600H has a lower price-per-gigabyte, >despite the FIREBALL_TM3200S is one of the cheapest SCSI units >available. My QUANTUM FIREBALL_TM2110A with Triton-1 IDE does 5572K/s writing with bonnie -s 64 on the fastest file system that I measured (ext2fs with a block size of 4K under FreeBSD; fs at offset 320MB) on a P5/133. 2.1GB Fireball_TM's are the same as 3.2MB ones except for fewer heads. >> won't get anywhere near the throughput of a SCSI drive if you can't >> schedule and have the drive reorder multiple transactions at a time. Right, IDE gives almost twice as much throughput with a Fireball_TM, at least if it is not slowed down by using DMA :-). (It seemed to be only slightly slower using DMA under Linux.) Of course, SCSI with busmastering DMA is better for systems that do lots of i/o. Such systems don't seem to be very common. E.g., freefall has averaged 141K/sec total since boot 5+ days ago. That's a whole 35K/sec per disk. It has only been 89.7% idle. I don't think the counters have overflowed. The counters have overflowed on hub. My home system has averaged 8K/sec per disk and 78.5% idle over one day. Bruce
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