From: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
To: James Harper <james.harper-NMzNsA1hOHcW+bLBXbPJGg@public.gmane.org>
Cc: "linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: 4K sectors
Date: Mon, 13 Aug 2012 14:12:27 -0700 [thread overview]
Message-ID: <20120813211227.GA6887@google.com> (raw)
In-Reply-To: <6035A0D088A63A46850C3988ED045A4B299F682F-mzsoxcrO4/2UD0RQwgcqbDSf8X3wrgjD@public.gmane.org>
On Mon, Aug 13, 2012 at 07:19:50AM +0000, James Harper wrote:
> I notice on my system that bcache presents 4K sectors to Linux. This is causing me problems with Windows on Xen using my PV drivers (problem = doesn't work). I haven't figured out if it's my PV drivers that don't tell Windows the right thing, or if Windows just doesn't like 4K sectors.
>
> Is the 4K sector thing intentional? I assume there is a performance improvement in doing so.
It is intentional, but it's configurable. It's mainly for devices that
don't support < 4k writes; there might also be a performance impact with
some SSDs but I'm sure it's slight.
You'll need to reformat - pass --block 512 to make-bcache. The backing
devices need to be reformatted too, but just rerunning make-bcache won't
touch any of the existing data.
>
> And what would be the performance impact if I just told Windows that it was dealing with 512 byte sectors (eg fake it)?
>
> Thanks
>
> James
> --
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prev parent reply other threads:[~2012-08-13 21:12 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-13 7:19 4K sectors James Harper
[not found] ` <6035A0D088A63A46850C3988ED045A4B299F682F-mzsoxcrO4/2UD0RQwgcqbDSf8X3wrgjD@public.gmane.org>
2012-08-13 21:12 ` Kent Overstreet [this message]
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