[DRBD-user] DRBD Dual Primary + GFS2 for redundant KVM hosts

Digimer lists at alteeve.ca
Fri Aug 25 22:01:00 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On 2017-08-25 03:37 PM, Gionatan Danti wrote:
> Il 25-08-2017 14:34 Digimer ha scritto:
>>
>> Our Anvil! project (https://www.alteeve.com/w/Build_an_m2_Anvil!) is
>> basically this, except we put the VMs on clustered LVs and use gfs2 to
>> store install media and the server XML files.
>>
>> I would NOT put the image files on gfs2, as the distributed locking
>> overhead would hurt performance a fair bit.
> 
> Hi, I contemplated using an active/active lvm-based configuration, but I
> would really like to use files as per VM disks.
> So, do you feel GFS2 would be inadequate for VM disk storage? What if a
> node crashes/reboots? Will GFS2 continue to work?
> 
> Thanks.

The overhead of clustered locking is likely such that your VM
performance would not be good, I think.

With raw clustered LVs backing the servers, you don't need cluster
locking on a per-IO basis, only on LV create/change/delete. Because LVM
is sitting on top of DRBD (in dual-primary), live-migration is no
trouble at all and performance is good, too.

GFS2, being a cluster FS, will work fine if a node is lost, provided it
is fenced succesfully. It's wouldn't be much of a cluster-FS otherwise. :)

-- 
Digimer
Papers and Projects: https://alteeve.com/w/
"I am, somehow, less interested in the weight and convolutions of
Einstein’s brain than in the near certainty that people of equal talent
have lived and died in cotton fields and sweatshops." - Stephen Jay Gould



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