Date: Mon, 3 Jan 2000 10:41:23 +1030 From: Greg Lehey <grog@lemis.com> To: R Joseph Wright <rjoseph@nwlink.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: some performance issues Message-ID: <20000103104123.H1528@freebie.lemis.com> In-Reply-To: <386FD085.93BFA305@nwlink.com> References: <386C3173.1D695393@3-cities.com> <386C543D.6E59C9DF@nwlink.com> <19991231104441.C2609@emu.sourcee.com> <386CE8AB.29A140B5@nwlink.com> <386CF9DC.B71A9887@3-cities.com> <386D3D3C.C92D02A3@nwlink.com> <386D5C88.B8257D45@3-cities.com> <386D8ABD.C2894A91@nwlink.com> <20000101160159.O1528@freebie.lemis.com> <386FD085.93BFA305@nwlink.com>
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On Sunday, 2 January 2000 at 14:26:13 -0800, R Joseph Wright wrote:
> Greg Lehey wrote:
>
>> iozone is not really a storage device testing program. Use rawio (in
>> the Ports Collection) for that: it bypasses the cache. Read carefully
>> the warnings which tell you that you should not use the write tests on
>> a file system which contains data you want to keep.
>>
>>> Kent, I tried that, only for me it worked doing "iozone 160". Here is
>>> my results:
>>>
>>> 11483869 bytes/second for reading
>>> 15155142 bytes/second for writing
>>
>> This is sequential access. You'll never get that in practice.
>>
>>> Is that really slow? It's nowhere near 33MB/second.
>>
>> 33 MB/s is the transfer rate from disk buffer to CPU. The transfer
>> rate off the platter is slower, and your speeds there look pretty
>> good. But remember that they're the ideal case.
>>
>>> I have a Maxtor 7000rpm with UDMA66 capabilities, although I'll have
>>> to wait for -STABLE to support that, and a new motherboard as well.
>>> I may recompile with the old flags just to see the difference.
>>
>> I'd be interested to see the difference, but I don't think it'll be
>> very much. Try both with rawio, and look at the random access
>> results, which are the only ones that count in practice.
>>
>> Greg
>
> I tried rawio, and got the following using flags 0xb0ffb0ff:
>
> Random Read Random Write
> ID K/sec /sec K/sec /sec
> anon 25352.3 1560 16548.4 1024
>
> With flags set at 0x80ff80ff, I got:
>
> K/sec /sec
> 12992.0 806
The results don't look very likely. Did you run them against the
block device? That doesn't do anything useful. I've just tried this
on an LVD drive and got:
Random read Sequential read Random write Sequential write
ID K/sec /sec K/sec /sec K/sec /sec K/sec /sec
da1 1650.5 103 1603.6 98
That does, in fact, look rather bad, but it's more typical for random
access.
> After that, it core dumped.
At what point? Where's the core?
> BTW, your book The Complete FreeBSD has been tremendously helpful! Thank
> you 8)
You're welcome.
Greg
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