Open Stack

For those who are interested we will discuss the disaster recovery 
use-cases and how to proceed toward the Juno summit on March 19 at 17:00 
UTC (invitation below)



Call-in: 
https://www.teleconference.att.com/servlet/glbAccess?process=1&accessCode=6406941&accessNumber=1809417783#C2 

Passcode: 6406941

Etherpad: 
https://etherpad.openstack.org/p/juno-disaster-recovery-call-for-stakeholders
Wiki: https://wiki.openstack.org/wiki/DisasterRecovery

Regards,
__________________________________________
Ronen I. Kat, PhD
Storage Research
IBM Research - Haifa
Phone: +972.3.7689493
Email: ronenkat at il.ibm.com




From:   "Luohao (brian)" <brian.luohao at huawei.com>
To:     "OpenStack Development Mailing List (not for usage questions)" 
<openstack-dev at lists.openstack.org>, 
Date:   14/03/2014 03:59 AM
Subject:        Re: [openstack-dev] Disaster Recovery for OpenStack - call 
for stakeholder



1.  fsfreeze with vss has been added to qemu upstream, see 
http://lists.gnu.org/archive/html/qemu-devel/2013-02/msg01963.html for 
usage.
2.  libvirt allows a client to send any commands to qemu-ga, see 
http://wiki.libvirt.org/page/Qemu_guest_agent
3.  linux fsfreeze is not equivalent to windows fsfreeze+vss. Linux 
fsreeze offers fs consistency only, while windows vss allows agents like 
sqlserver to register their plugins to flush their cache to disk when a 
snapshot occurs.
4.  my understanding is xenserver does not support fsfreeze+vss now, 
because xenserver normally does not use block backend in qemu.

-----Original Message-----
From: Bruce Montague [mailto:Bruce_Montague at symantec.com] 
Sent: Thursday, March 13, 2014 10:35 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] Disaster Recovery for OpenStack - call for 
stakeholder

Hi, about OpenStack and VSS. Does anyone have experience with the qemu 
project's implementation of VSS support? They appear to have a 
within-guest agent, qemu-ga, that perhaps can work as a VSS requestor. 
Does it also work with KVM? Does qemu-ga work with libvirt (can VSS 
quiesce be triggered via libvirt)? I think there was an effort for qemu-ga 
to use fsfreeze as an equivalent to VSS on Linux systems, was that done? 
If so, could an OpenStack API provide a generic quiesce request that would 
then get passed to libvirt? (Also, the XenServer VSS support seems 
different than qemu/KVM's, is this true? Can it also be accessed through 
libvirt?

Thanks,

-bruce

-----Original Message-----
From: Alessandro Pilotti [mailto:apilotti at cloudbasesolutions.com]
Sent: Thursday, March 13, 2014 6:49 AM
To: openstack-dev at lists.openstack.org
Subject: Re: [openstack-dev] Disaster Recovery for OpenStack - call for 
stakeholder

Those use cases are very important in enterprise scenarios requirements, 
but there's an important missing piece in the current OpenStack APIs: 
support for application consistent backups via Volume Shadow Copy (or 
other solutions) at the instance level, including differential / 
incremental backups.

VSS can be seamlessly added to the Nova Hyper-V driver (it's included with 
the free Hyper-V Server) with e.g. vSphere and XenServer supporting it as 
well (quescing) and with the option for third party vendors to add drivers 
for their solutions.

A generic Nova backup / restore API supporting those features is quite 
straightforward to design. The main question at this stage is if the 
OpenStack community wants to support those use cases or not. Cinder 
backup/restore support [1] and volume replication [2] are surely a great 
starting point in this direction.

Alessandro

[1] https://review.openstack.org/#/c/69351/
[2] https://review.openstack.org/#/c/64026/


> On 12/mar/2014, at 20:45, "Bruce Montague" <Bruce_Montague at symantec.com> 
wrote:
>
>
> Hi, regarding the call to create a list of disaster recovery (DR) use 
cases ( 
http://lists.openstack.org/pipermail/openstack-dev/2014-March/028859.html 
), the following list sketches some speculative OpenStack DR use cases. 
These use cases do not reflect any specific product behavior and span a 
wide spectrum. This list is not a proposal, it is intended primarily to 
solicit additional discussion. The first basic use case, (1), is described 
in a bit more detail than the others; many of the others are elaborations 
on this basic theme.
>
>
>
> * (1) [Single VM]
>
> A single Windows VM with 4 volumes and VSS (Microsoft's Volume 
Shadowcopy Services) installed runs a key application and integral 
database. VSS can quiesce the app, database, filesystem, and I/O on demand 
and can be invoked external to the guest.
>
>   a. The VM's volumes, including the boot volume, are replicated to a 
remote DR site (another OpenStack deployment).
>
>   b. Some form of replicated VM or VM metadata exists at the remote 
site. This VM/description includes the replicated volumes. Some systems 
might use cold migration or some form of wide-area live VM migration to 
establish this remote site VM/description.
>
>   c. When specified by an SLA or policy, VSS is invoked, putting the 
VM's volumes in an application-consistent state. This state is flushed all 
the way through to the remote volumes. As each remote volume reaches its 
application-consistent state, this is recognized in some fashion, perhaps 
by an in-band signal, and a snapshot of the volume is made at the remote 
site. Volume replication is re-enabled immediately following the snapshot. 
A backup is then made of the snapshot on the remote site. At the 
completion of this cycle, application-consistent volume snapshots and 
backups exist on the remote site.
>
>   d.  When a disaster or firedrill happens, the replication network 
> connection is cut. The remote site VM pre-created or defined so as to 
use the replicated volumes is then booted, using the latest 
application-consistent state of the replicated volumes. The entire VM 
environment (management accounts, networking, external firewalling, 
console access, etc..), similar to that of the primary, either needs to 
pre-exist in some fashion on the secondary or be created dynamically by 
the DR system. The booting VM either needs to attach to a virtual network 
environment similar to at the primary site or the VM needs to have boot 
code that can alter its network personality. Networking configuration may 
occur in conjunction with an update to DNS and other networking 
infrastructure. It is necessary for all required networking configuration 
to be pre-specified or done automatically. No manual admin activity should 
be required. Environment requirements may be stored in a DR configuration 
o r database associated with the replication.
>
>   e. In a firedrill or test, the virtual network environment at the 
remote site may be a "test bubble" isolated from the real network, with 
some provision for protected access (such as NAT). Automatic testing is 
necessary to verify that replication succeeded. These tests need to be 
configurable by the end-user and admin and integrated with DR 
orchestration.
>
>   f. After the VM has booted and been operational, the network 
> connection between the two sites is re-established. A replication 
> connection between the replicated volumes is restablished, and the 
> replicated volumes are re-synced, with the roles of primary and 
> secondary reversed. (Ongoing replication in this configuration may 
> occur, driven from the new primary.)
>
>   g. A planned failback of the VM to the old primary proceeds similar to 
the failover from the old primary to the old replica, but with roles 
reversed and the process minimizing offline time and data loss.
>
>
>
> * (2) [Core tenant/project infrastructure VMs]
>
> Twenty VMs power the core infrastructure of a group using a private 
cloud (OpenStack in their own datacenter). Not all VMs run Windows with 
VSS, some run Linux with some equivalent mechanism, such as qemu-ga, 
driving fsfreeze and signal scripts. These VMs are replicated to a remote 
OpenStack deployment, in a fashion similar to (1). Orchestration occurring 
at the remote site on failover is more complex (correct VM boot order is 
orchestrated, DHCP service is configured as expected, all IPs are made 
available and verified). An equivalent virtual network topology consisting 
of multiple networks or subnets might be pre-created or dynamically 
created at failover time.
>
>   a. Storage for all volumes of all VMs might be on a single storage 
backend (logically a single large volume containing many smaller 
sub-volumes, examples being a VMware datastore or Hyper-V CSV). This 
entire large volume might be replicated between similar storage backends 
at the primary and secondary site. A single replicated large volume thus 
replicates all the tenant VM's volumes. The DR system must trigger quiesce 
of all volumes to application-consistent state.
>
>   b. This environment needs to deal with failures of the primary 
datacenter (as when a trenching tool cuts its connection to the internet), 
routine firedrill tests that perform failover and failback, and planned 
migration.
>
>   c. VSS or fsfreeze may be expected to fail for some VMs and policies 
and SLAs need to contend with this and alert admins for manual follow-up.
>
>   d. Network bandwidth used for replication needs to be throttled so as 
not to overly disrupt the private cloud's gateway capacity.
>
>   e. DR replication needs to deal with intermittent network replication 
failure and recover gracefully. In case of a known network issue, such as 
maintenance, it needs to be possible for the admin to explicitly suspend 
network replication. Replication I/O is then logged locally at the primary 
site in some fashion. The remote site needs to stay replication ready, but 
failover does not occur. When the network issue is over, replication 
resumes, perhaps recovering via a log, a map of updated blocks, or an 
equivalent technique. In this example the RPO window is deliberately 
ignored and allowed to grow until replication is resumed by the admin.
>
>   f. This tenant requires encryption of network replication traffic.
>
>   g. Cost accounting and chargeback is required.
>
>
>
> * (3) [Multi-tier app infrastructure]
>
> A tenant has a service consisting of 8 multi-tier apps that each consist 
of 3 to 5 VMs, with each VM having 2 to 4 disks. Replication snapshots 
need to be made of the volumes in an application-consistent way across all 
the volumes of all the VMs in all the multi-tier apps. Again, these 
volumes may exist on a single large volume or datastore, perhaps 
simplifying creation of the cross-VM application consistency snapshot. Not 
all of the VMs in a multi-tier app may need to be quiesced, some may be 
stateless and simply need to be recovered to a running state.
>
> a. This tenant requires that 3 of the multi-tier apps failover to one 
remote OpenStack site and the other 5 multi-tier apps failover to a 
different remote site than the first.
>
> b. This tenant weekly performs a non-disruptive test-bubble failover 
test. Real failover is not triggered. Instead, all the multi-tier app VMs 
that would boot upon failure are booted (from their latest snapshots on 
the secondary), but the VM's virtual network environment on the secondary 
is isolated from external networking. Test bubbles at the two OpenStack 
remote sites may need to be connected via some VPN/tunnel or equivalent 
without manual admin activity.
>
>
>
> * (4) [Tenant failover]
>
> An OpenStack tenant has 40 VMs, relatively lightly loaded, used for 
development. The VMs do not contain VSS, qemu-ga, or standard tools (they 
may be running any Linux distro, some may be running Plan9, the tenant may 
be doing Linux kernel development (that is, the VMs can be anything)). A 
remote OpenStack deployment needs to exist so that in event of loss of the 
primary OpenStack site, the tenant can continue development. In addition 
to volume replication as in (1), subject to policies and SLAs, cold 
migration may be performed on a VM's volumes upon shutdown (or dismount) 
and tenant end-users can explicitly request replication of a volume that 
is in an application-consistent state (when they have quiesced it by VSS, 
dismount, or equivalent).
>
> a. Being down for a short period may be acceptable to this tenant. If 
all the hosts on the primary site are rebooted, for instance, due to power 
failure, it is the operators choice to fail over or not. If the operator 
chooses not to fail over, upon reboot of the VM's at the primary site, any 
established replication should automatically be continued.
>
>
>
> * (5) [Scale-out workload]
>
> A tenant has a Cassandra (or Hadoop or similar type of system) 
consisting of 75 VMs. Use is bursty. The system is used by a 
pharmaceutical company for design work. Loss of a week's work can be 
repeated, but weekly replication is mandatory. The application itself may 
provide some form of built-in geo-replication. Some controller-type VMs 
may need to be replicated as in (1). Other VMs may partner with replica 
VMs for explicit application data replication. For weekly replication of 
Cassandra data, Cassandra user-level snapshots are made into replicated 
volumes attached to each Cassandra VM. Replication is periodic with 
respect to the last replication event, that is, only data changed since 
the last replication event is sent.
>
>   a. The tenant requires use of a particular aggregated network link for 
replication.
>
>   b. The tenant requires custom integration with the DR replication 
workflow to quiesce Cassandra via user-level commands and scripts 
developed by the end-user.
>
>   c. Initial synchronization of replicated primary and secondary volume 
need not be over a network link. Secondary volumes can be created 
initially from physical disks or backups physically moved to the secondary 
site.
>
>
>
> * (6) [Degraded-mode Mission-critical single VM]
>
> This single VM use case is similar to (1), but when a network 
> partition occurs between the primary and secondary OpenStack sites, 
> with both sites remaining up, the primary VM remains operational while 
> the secondary replica VM also comes online. Both VMs operate in a mode 
> that resembles replication with a momentary network fault, logging 
> their would-be replication traffic for continuation when the network 
> comes back. When network connectivity is reestablished, one site again 
> becomes the primary and differences in the VM's volumes can optionally 
> (as controlled by policy) be reconciled. (In a simple case, each site 
> might have its own dedicated volume partition or attached volume with 
> its latest state.)
>
>
>
> * (7) [Self-contained application volume]
>
> A cinder volume contains a complete database application, including the 
database and all binaries and configuration files. Replication of the 
entire VM to which this volume is attached is not needed. The VM and  its 
configuration can be recreated on demand at the remote site and attached 
to the replicated application volume. The DR system still needs to 
orchestrate the process and create or manage the required network 
environment. A simple DR strategy can be used in which the volume is 
quiesced on the primary, a volume snapshot taken, the volume unquiesced 
(enabling the VM to continue running), and a backup is then made of the 
snapshot. Backups can be transported by whatever means to the DR site, 
where the volume can be restored to its state at time of snapshot.
>
>
>
> * (8) [Stateless]
>
> No volumes and VMs need to be replicated, as VMs and their configuration 
can be recreated on demand, using configuration tools, and application 
data is accessed over the wide-area network (NFS or object store). The DR 
process still has to orchestrate creating the VMs, running configuration 
tools to populate them, creating the network environment, and booting VMs 
in required order.
>
>
>
> * (9) [Site Evacuation]
>
> The holy grail, automatic planned migration of the workload and data 
from one cloud-scale datacenter to another (or a set of others). In 
practice, likely to include admins in-the-loop. At both tenant-scale and 
entire datacenter scale. The entire cloud datacenter is expected to go 
offline for an extended period (the hurricane scenario).
>
>
>
> -bruce
>
>
> _______________________________________________
> OpenStack-dev mailing list
> OpenStack-dev at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev

_______________________________________________
OpenStack-dev mailing list
OpenStack-dev at lists.openstack.org
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev

_______________________________________________
OpenStack-dev mailing list
OpenStack-dev at lists.openstack.org
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev

_______________________________________________
OpenStack-dev mailing list
OpenStack-dev at lists.openstack.org
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