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Disaster Recovery Mirroring System (D.R.M.S.)
The
Challenge
The risks and the devastating effects of disasters resulting in
computer downtime are obvious and always pose a pressing issue to
any business running critical applications. Business orgranizations
demand 100% fault tolerance and continuous availability of their
computing systems. Relying on traditional, full system backups means
that any critical data and transactions executed after the last
system backup are lost forever. The use of traditional backups also
means that data at the remote site always lags behind, so that the
remote computers can not be used for online production processing
and can only be utilized in course of a disaster-recovery scenario.
For this reason, these vital and expensive resources are idle while
the primary computer, in many cases, is over-loaded and suffering
from deteriorated performance.
What
Is DRMS?
DRMS is a software solution that provides reliable, bi-directional
real-time data backup and mirroring over existing Stratus networks.
At any given time, all critical remote databases are identical to
the primary database, which ensures rapid and reliable application
recovery. Networked computers mirror each other providing flexible,
scaleable load-balancing solution utilizing the full computing capacity
of the hardware at both the primary and remote locations. DRMS replicates
sequential, fixed, relative and stream files (including transaction-protected
files) as well as, one-way-server-queue and message queues. DRMS
dynamically detects and replicates newly created critical files
so that no configuration changes are necessary. The internal design
of DRMS puts great emphasis on protecting the business application
and on preserving the primary computer's current performance. DRMS
is external to the business application and requires absolutely
no application or any software changes - its operation is completely
transparent to the user.
Technical
expertise and Support
"SoftMark worked closely with Stratus to ensure their systems
operated in concert to provide the highest levels of service for
Tosco." Stratus Computer news brief, September 1999.
"The product's reliability and SoftMark's extraordinary responsiveness
to our business needs and support questions has made the implementation
of our Disaster-Recovery plans an easy, pleasant and trouble-free
experience." Anders Carlsson, ICA
"We rate Application Resources (the distributor of DRMS) and SoftMark (developer/owner) as our best vendors in terms of problem/issue turnaround. Even after-hours, there is no discernible drop-off in resolution speed "). It became very apparent from our discussions that they really understood the issues behind disaster recovery. Andy Orrock, Tosco Corporation
"SoftMark's technical support and responsiveness is outstanding. Their continued advice and close involvement with our project has made the integration of this product into a very large production system a manageable task." Alex Tulchinsky, AOL
"SoftMark has provided us with a high level of support and has always been responsive to our business needs." Todd Brown, Sherwood Securities
Hands-off
operations
DRMS is designed to run 24x7 without any human intervention. DRMS
dynamically manages all aspects of error detection, handling and
recovery including alternate routing and communication line switching
- always utilizing the entire network bandwidth.
"The DRMS product has been stable and has worked reliably since
we first installed it in August 97. " Anders Carlsson, ICA
Scalability
As a software-only solution, DRMS offers total configuration flexibility
and scalability. Any number of modules can mirror each other. The
administrator can select and identify critical data files, directories
or disks - all within DRMS' configuration. DRMS can simultaneously
mirror critical data in any direction (A-to-B, B-to-A, B-to-C etc.).
DRMS supports all VOS platforms and all VOS releases.
Simplicity
DRMS requires no application changes whatsoever. It is extremely
simple to learn, implement and operate on a daily basis and requires
no specific training. The implementation phase of the software can
be completed within a few days, once all critical data files or
directories have been identified and listed in DRMS' configuration
table (DRMS uses only one TIN file!). DRMS requires no additional
hardware as it utilizes existing networks and supports both TCP-IP
and X.25 connections.
"The complete DRMS implementation took about 2 weeks. The installation
of the product and the learning curve was done within only one day.
Most of the time was spend on analyzing which critical files to
mirror, fine-tuning our configuration and running benchmark tests."
Anders Carlsson, ICA
"The product was easy to configure and implement … there is nothing more that one table to configure and we were able to do that with simple phone support." Andy Orrock, Tosco Corporation
Batch
Commands
DRMS replicates VOS internal commands, such as copy_file, move_file,
rename, create_file etc. so that any after-hours batch cycles and
command-macros are also mirrored accurately at the remote site.
Monitoring
and reporting facilities
DRMS includes a robust and user-friendly administrator interface.
The operator can monitor the system and all aspects of the data
mirroring activities - number of I/Os, queuing operations, transaction
throughput, processing rate etc. These monitors provide, at all
times great sense of control over the system. DRMS maintains and
reports activities both on system-level as well as on a per-file
basis down to the lowest details of how many I/O operations were
made on each critical file broken down by I/O type (write/update/delete
etc.)
Performance
Since most of the processing takes place at the target system, DRMS
has practically no impact on performance of the primary (sending)
computer.
"Performance of DRMS is terrific - data is mirrored immediately
over our 1 MB pipe. We attribute much of the gain in our performance
efficiency to the fact that we deployed DRMS to replace a 'homegrown'
mirroring solution that was patched together by our OLTP vendor.
There is not any sign of page faulting. I rate that as very little
overhead, considering that we're updating 2-3 files for each transaction
and running at about 14-15 TPS when I took this measurement."
Andy Orrock, Tosco Corporation
"We were also surprised with the results of our performance tests - during normal system load the overhead of DRMS is not noticeable at and, and during peak time (25 transactions/per second) we've measured an overhead of no more than 5%." Anders Carlsson, ICA
How
does DRMS work?
During run-time, DRMS intercepts all I/O operations performed on
files marked by the system administrator as "critical".
After the I/O operation is completed, DRMS passes the information
to the DRMS Server for transmission to the target system. The corresponding
DRMS server on the target computer collects these messages and executes
the I/O operation within the remote databases. The only additional
work that a mirrored operation requires is the sending of the message
to the DRMS queue. The entire operation is therefore completed with
minimal impact on the end-user's program.
Open
Architechture
Based on known data layouts and user-provided templates, DRMS can
be used to convert any VOS data into standard text-only formats
such as comma-delimited, XML etc. Such output is then transmitted
to remote ODBC databases or written to local VOS files or queues
for further processing.
S$-Usage
Monitor
The s$-Usage Monitor provides a real-time view of the application's I/O activities.
Frequently
asked questions
What
kind of system overhead should I expect?
Overhead depends entirely on user application and mirroring requirements:
the rate of I/O, average buffer size and number of critical applications
and files. Typically, you should expect not more than 5% overall
system overhead.
Is
it really that simple?
Not at all! Achieving complete, reliable and efficient data mirroring
and planning for Disaster Recovery is not an easy or simple matter.
For this reason, keeping-it-simple was our most important objective
in the DRMS design:
The user must not struggle with the new product. We provide sample configuration, start-up macros and a Demo application with its complete source code.
DRMS must be installed, configured and should demonstrate real-time mirroring for the Demo application within 5-10 minutes!The user is expected to understand the mechanics of the software within 30 minutes.
Do
you provide any on-site assistance for DR implementations?
Absolutely! At your request we'll conduct an on-site study for the
purpose of setting up a Hot Backup facility for your critical application.
We will review all hardware involved, analyze system performance
and utilization (CPU, Disk space, I/O activities, Comms., etc),
application load. We will also review all your management and operation
procedures. Our detailed report will provide you with a step by
step plan for setting up and implementing your Hot Backup and all
other application recovery procedures. Typically, the scope of this
study goes beyond Hot Backup analysis as it includes analysis of
system performance and a detailed plan for securing and automating
your day to day Stratus operations to reduce the likelihood and
risks of system failures.
What
happens to mirroring when my communication line is down? What happens
to my application?
The product is designed to protect the primary application - failed
mirroring will have no affect on your application. When communication
is restored, DRMS will automatically continue to mirror from the
point of failure.
Can
DRMS mirror our VM (virtual memory) region updates?
Absolutely. Many users of TCAM's software have asked us for this
feature. We have a TCAM-specific design that allows VM mirroring
with 50% less mirroring related I/O and network traffic. For a more
detailed overview, please contact our technical support.
Am
I required to run the primary application for the company on the
Hot Backup system? If so, what is the main purpose?
Normally, the DRMS Server will perform all I/O on the Hot Backup
module, so it is absolutely NOT required to run the application.
However, if software licensing is not an issue, there may be cases
for executing the application on the backup machine.
What
are, if any, the hardware requirements? Does the Primary and Hot
Backup systems have to be running on the same processor type (Cisc/Risc/Continuum)?
Absolutely not! The only requirement is that you will have sufficient
communication bandwidth to the Backup site and a platform that will
be able to keep up with the primary module.
Can
I specify files, queues, directories or logical disks?
DRMS has no concept of logical disks. The configuration layer allows
you to select files and queues (1-way-server-queues and message-queues).
Star-names are also supported, so if you need to mirror all files
in a specific directory.
I
am using two production sites and maintain one backup site for both.
Will I be able to mirror the two production systems to the backup
site?
DRMS can be easily configured to accept input from multiple systems.
The only requirement is sufficient bandwidth and resources at the
Backup site to carry the load.