Architecture

Whether you are dealing with disk I/O in reading the data from the disks, or CPU for compressing or encrypting the data (or both- remember to compress and then encrypt!), or network for transferring the data to a backup server, the added load of a backup on your production servers is unwelcome. For this reason, the period of time during which backups can be made, aka. backup window, may be limited- even severely.

You may say, "It only takes me X hours to do a full backup of everything", but over time backup windows are notorious for becoming too small. Backups are split over multiple days, technologies upgraded, etc. When planning a backup strategy, my approach is to eliminate the backup window altogether- that is do whatever you can to take the backup off the production hardware altogether.

Storage Snapshots are one method for taking the production servers out of the backup equation. By creating a consistent, point in time snapshot on your storage, and mounting it on your backup server, you can backup your data using your backup server's resources while your production servers continue as usual.

Caveats of this method in general are:

November 16, 2009

UPDATE: No ZFS Support for Replication Manager in the near future

Using storage level snapshots can be used to run backups without directly requiring resources from the original host.

EMC Replication Manager coordinates the creation of application consistent snapshots across all the hosts in your network. It handles scheduling creation/expiration of snapshots,  mounting and unmounting from backup servers, etc. from a single console.

Although it is not tightly integrated into EMC Networker like the similar Networker PowerSnap module, it can be used to start a backup process after taking a new snapshot and it has the capability to manage snapshots unrelated to backups from a GUI.

While the data sheet claims support for Solaris, there are several caveats which I have run into.

November 16, 2009

When discussing availability of a service, it is common to hear the term "Five Nines" referring to a service being available 99.999% of the time but "Five Nines" are relative. If your time frame is a week, then your service can be unavailable for 6.05 seconds whereas a time frame of a year, allows for a very respectable 5.26 minutes.

In reality, none of those calculations are relevant because no one cares if a service is unavailable for 10 hours, as long as they aren't trying to use it. On the other hand, if you're handling 50,000 transactions per second, 6.05 seconds of unavailability could cost you 302,500 transactions and no one cares if you met your SLA.

This problem is one I've come up against a number of times in the past and recently even more and the issue is orders of magnitude in IT. The larger the volume of business you handle, the less relevant the Five Nines become.

November 04, 2009

Reporting projects are the kind of projects which never seem to end. After a couple iterations I've come to the following conclusions:

1. Absolutely no reports should run on a production database.
2. Moving/aggregating data from a production database to a reporting database using ETL tools prone to synchronization issues and pretty unreliable.
3. The best option is to set up real time replication of the data and build additional views on that.

Unfortunately, if you need to get data from heterogeneous databases, ie. Oracle, MySQL, SQL Server, etc. into a single reporting database, replication is not a simple solution. If you are running expensive database software in production, it may not be cost effective to run the same database for reporting.

Of course there are cross database replication solutions like Golden Gate or SharePlex but they are very expensive. I had already given up on getting data from Oracle into MySQL for reports when I stumbled across Tungsten Replicator.

October 25, 2009

What is a Systems Architect?

Systems Architects have years of experience in the various parts of the systems they work with. Most probably, they specialize in a specific area area of expertise where they began their careers, but have since expanded their knowledge by learning from their colleagues and from life's lessons. To get to their position, they have proven their ability to analyze and understand the needs and constraints of the business they work in. They are responsible for deciding what technologies will provide the best solutions for a business, how to integrate them with existing systems, and how to retire them when they are obsolete.

There are several flavors of Systems Architects.

August 02, 2009