Re: [Nbd] BCache with NBD is it possible?
- To: nbd-general@lists.sourceforge.net
- Subject: Re: [Nbd] BCache with NBD is it possible?
- From: Goswin von Brederlow <goswin-v-b@...186...>
- Date: Thu, 13 Mar 2014 12:06:53 +0100
- Message-id: <20140313110653.GC13151@...1266...>
- In-reply-to: <1393317009.26501.10.camel@...1346...>
- References: <1393245985.18926.13.camel@...1346...> <CAECXXi6wg_FogVZECLrK79BpRh7VMmGVTa-covkYuQGBVrOEkQ@...18...> <1393317009.26501.10.camel@...1346...>
On Tue, Feb 25, 2014 at 09:30:09AM +0100, Juan Antonio Martinez wrote:
> El lun, 24-02-2014 a las 09:59 -0500, Paul Clements escribió:
> > It certainly should work. bcache is a generic block device cache. That
> > said, I have not actually tried it with nbd, so maybe there's some bug
> > preventing it from working?
> >
> Well, AFAIK the main problem is that nbd real device is a file with an
> in-built squashfs that resides in a remote server...
>
> That is: I can create my local cache device by mean of "make-bcache
> -C /dev/sda1" but I cannot declare caching device by mean of
> "make-bcache -B /dev/nbd0" because returns "device busy" error.... thus
> cannot attach it to my local cache device .
>
> ¿Any way to bypass this? Perhaps I'm missing something about how bcache
> works... :-(
>
> Thanks for your attention. Cheers
> Juan Antonio
>
> > On Mon, Feb 24, 2014 at 7:46 AM, Juan Antonio Martinez
> > <jantonio@...1345...> wrote:
> > Hi all:
> > I have 250+ ubuntu 13.10 ltsp fat clients. As client hardware
> > is a "bit
> > obsolete" and don't want to buy extra memory for those
> > computers, we are
> > studying some configurations to improve performance.
> >
> > As on 13.10 BCache comes in the kernel mainline we'll want to
> > use local
> > client's disk as cache for nbd device.
> >
> > Is it possible? BCache documentation suggest it, but didn't
> > find any
> > tutorial/guide. Everything I got is a message like
> > "Device /dev/nbd0 is
> > not a partition, a logical volume or a LUKS volume" when using
> > "blocks
> > to-cache" commannd
> >
> > Thanks in advance
> > Juan Antonio
"device busy" error sounds like you have the nbd0 already mounted. You
need to setup bcache before mounting it, maybe from an initramfs.
"Device /dev/nbd0 is not a partition, a logical volume or a LUKS
volume" would indicate that the tool expects device names to match a
certain pattern, like sd[a-z][1-9], and does not know about nbd0.
Which is a bit stupid to do since the name is totaly arbitrary. Check
the source for where and why it generates that error and fix that.
MfG
Goswin
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