[DRBD-user] Single versus multiple DRBD devices

[Dan Barker]

> -----Original Message-----
> From: Bart Coninckx [mailto:bart.coninckx at telenet.be]
> Sent: Friday, April 18, 2014 2:55 PM
> To: Dan Barker
> Cc: drbd-user at lists.linbit.com
> Subject: Re: [DRBD-user] Single versus multiple DRBD devices
> 
> 
> On 31 Mar 2014, at 13:59, Dan Barker <dbarker at visioncomm.net> wrote:
> 
> >> -----Original Message-----
> >> From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-
> >> bounces at lists.linbit.com] On Behalf Of Bart Coninckx
> >> Sent: Monday, March 31, 2014 6:51 AM
> >> To: Arnold Krille
> >> Cc: drbd-user at lists.linbit.com
> >> Subject: Re: [DRBD-user] Single versus multiple DRBD devices
> >>
> >>
> >> On 28 Mar 2014, at 22:04, Arnold Krille <arnold at arnoldarts.de> wrote:
> >>
> >>> On Fri, 28 Mar 2014 10:40:28 +0100 Bart Coninckx
> >>> <bart.coninckx at 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 at 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