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List:       drbd-user
Subject:    Re: [DRBD-user] Single versus multiple DRBD devices
From:       Dan Barker <dbarker () visioncomm ! net>
Date:       2014-04-19 21:16:01
Message-ID: 3896ab25fbdd4682bb698281daac38b6 () BN1PR04MB060 ! namprd04 ! prod ! outlook ! com
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> -----Original Message-----
> From: Bart Coninckx [mailto:bart.coninckx@telenet.be]
> Sent: Friday, April 18, 2014 2:55 PM
> To: Dan Barker
> Cc: drbd-user@lists.linbit.com
> Subject: Re: [DRBD-user] Single versus multiple DRBD devices
> 
> 
> On 31 Mar 2014, at 13:59, Dan Barker <dbarker@visioncomm.net> wrote:
> 
> > > -----Original Message-----
> > > From: drbd-user-bounces@lists.linbit.com [mailto:drbd-user-
> > > bounces@lists.linbit.com] On Behalf Of Bart Coninckx
> > > Sent: Monday, March 31, 2014 6:51 AM
> > > To: Arnold Krille
> > > Cc: drbd-user@lists.linbit.com
> > > Subject: Re: [DRBD-user] Single versus multiple DRBD devices
> > > 
> > > 
> > > On 28 Mar 2014, at 22:04, Arnold Krille <arnold@arnoldarts.de> wrote:
> > > 
> > > > On Fri, 28 Mar 2014 10:40:28 +0100 Bart Coninckx
> > > > <bart.coninckx@telenet.be> wrote:
> > > > > 	All,
> > > > > 
> > > > > 
> > > > > building a storage cluster which will offer SCST targets. These will
> > > > > be LVM based (nested LVM probably). In terms of performance, what is
> > > > > the most optimal strategy: one big DRBD device where the different
> > > > > Logical Volumes are installed on or a DRBD device per LV? If a resync
> > > > > needs to be done, the latter will probably better, as it allows us to
> > > > > choose which devices should be resynced first.
> > > > 
> > > > I do have several drbd volumes instead of one big. Then you can
> > > > choose which ones to sync first. And if your volumes are on different
> > > > disks, the order can be defined to sync volumes from each disk one
> > > > after the other but volumes from different disks in parallel. That way
> > > > one can max out a 2x10G connection with three volumes from three disks
> > > > all reading/writing sequential, instead of the disk stepping in its
> own
> > > > way by reading from several volumes on the same disk while the other
> > > > disks are idle...
> > > > 
> > > > And several drbd-volumes can fail-over individually.
> > > > 
> > > > Have fun,
> > > > 
> > > > Arnold
> > > 
> > > 
> > > Sounds reasonably! Thank you for your input!
> > > 
> > > BC
> > > 
> > 
> > What Bart is suggesting is matching your drbd definition to your
> physical environment. Your OP was about the logical environment. You'll
> probably have a combination of factors drive your design. For example, I
> have four DRBD resources servicing about 20 VMs. The four DRBD resources
> mirror my physical environment and the VMs are spread around on these four
> devices to minimize the impact of a failure or slow-down on any one.
> > 
> > Dan
> > 
> > _______________________________________________
> > drbd-user mailing list
> > drbd-user@lists.linbit.com
> > http://lists.linbit.com/mailman/listinfo/drbd-user
> 
> 
> Dan,
> 
> what do you mean by "DRBD resources mirroring your physical environment"?
> 
> 
> Cheers,
> 
> BC

I thought that was very clear. I have four storage devices, /dev/sdb through \
/dev/sde. So, I have four drbd devices, drbd0 through drbd3. There is a one-to-one \
mapping from my physical devices to drbd resources. This is certainly not the only \
way to do it; it's just what I have chosen.

hth

Dan
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