Why bother over bits?

I have a customer that recently experienced the tense situation of one of their most crucial Oracle production databases running out of disk space. They had archive logs that were growing larger with the amount of access/updates that were occuring and the logs were starting to chew up some of their already scarce space. While not involved in their OLTP oracle environment, I observed their DBA group manage these Oracle instances and had some thoughts intended to broaden the perspective of groups in similar situations.

The rate of archive log growth peaked at 1 gigabyte/hr (gb). They keep 8 days of archive logs so figure there could be a maximum log requirement of 192 (24 hrs/day). This is the maximum because it assumes that all periods behave like the peak which will almost certainly not be the case. Ok, so we’ve now determined a very conservative maximum log storage requirement of (round up) 200gb. Setting aside their specifics for a second, perhaps we generalize:

My advise to DBA groups out there is that DISK SPACE IS CHEAP, over provision liberally and ADD MORE WHENEVER POSSIBLE.

Why?

  • There is no cost for Oracle to use more space. Oracle is licensed on a CPU/user basis and there is no metric that is directly affected by the amount of storage in terms of the Oracle software cost.
  • Backup applications don’t store unused disk space. The cost of unused over provisioned disk space is just that. The multiplier effect that is often determined for backup (full/incrementals/etc) do not apply for over provisioned unused disk space.
  • Disk Space is Cheap. Disk Space is Cheap. Disk space is Cheap.
  • Disk Space can be VERY cheap. Google has established an operational miracle with fast, redundant, massively scalable disk space costs them approximately $2.33/gb on an annual basis! WOW!

    According to resources mentioned, mirrored fast disk space can be procured for $2.33 to $2.60 per gigabyte on an annual basis. Assuming that most IT departments can’t achive these great operational efficiencies double that number so that we paid a bit extra for some vendor provided services/training/packaging. At $5.20/yr for a gigabyte my customer could have purchased some peace of mind for approximately $1000/yr. If you look at the operational budgets for these systems and applications you’d understand how nominal a figure this becomes…

    The number of hours lost to clients, admin time in patchwork to make the gigabytes stretch, DBA time to change DB parameters, and the list goes on… It’s just not worth it when, you guessed it, DISK SPACE IS CHEAP!

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