Date: Tue, 15 Jan 2013 17:09:23 -0500 From: Karim Fodil-Lemelin <fodillemlinkarim@gmail.com> To: freebsd-hackers@freebsd.org Subject: Re: IBM blade server abysmal disk write performances Message-ID: <50F5D393.10704@gmail.com> In-Reply-To: <CAJ-VmomK2VvokDmZa1FsHqDs0xxA7UpQNGQBiqCLf8Jysw0_9g@mail.gmail.com> References: <CAA3ZYrACHLU-4OyhLdD%2BmfCDR_kubBg-AiVcopL-skqDurE7YA@mail.gmail.com> <50F5BC08.1060700@gmail.com> <CAJ-VmomK2VvokDmZa1FsHqDs0xxA7UpQNGQBiqCLf8Jysw0_9g@mail.gmail.com>
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On 15/01/2013 3:55 PM, Adrian Chadd wrote: > You're only doing one IO at the end. That's just plain silly. There's > all kinds of overhead that could show up, that would be amortized over > doing many IOs. > > You should also realise that the raw disk IO on Linux is by default > buffered, so you're hitting the buffer cache. The results aren't going > to match, not unless you exhaust physical memory and start falling > behind on disk IO. At that point you'll see what the fuss is about. > To put is simply and maybe give a bit more context, here is what we're doing: 1) Boot OS (Linux or FreeBSD in this case) 2) dd some image over to the SAS drive. 3) rinse and repeat for X times. 4) profit. In this case if step 1) is done with Linux we get 100 times more profit. I was wondering if we could close the gap. Karim.
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