Neil Barton

Friday, November 27, 2009

7p per Gbyte per month for backup?

An interesting advert yesterday in The Times in the UK. IBM are advertising a hardware/software backup server bundle in a full-page advert with a prominent price marked "From" GBP 334 (USD 534) per month. Actually it's a three year cost of GBP 10,929 (USD 17,486), which over three years comes out closer to GBP 305/month - the extra 10% must be either financing costs or the evaluation service mentioned below.

It's aimed at mid-sized businesses, and the package seems to consist of:
- an evaluation of where you are now
- A SystemX server running Tivoli Fastback, hardware maintenance included.
- A DS3300 storage array.

A lot of backup services are priced per Gbyte per month, not per server. If we could work out how much storage the bundle provides, we could calculate this. This turns out to depend on what size disks you put in the storage array, and how fully you populate it. IBM's web site suggests that the 172631X part number mentioned in the advert comes with 12 disks and scales to 4.8 Tbytes with 1 Tbyte disks. Dividing 4.8 Tbytes into the monthly price gives you GBP 0.07 per Gbyte per month. Call it 11 US cents/Gbyte/month.

I have some comments about this number which explain why your price per Gbyte per month might be completely different.

1. In the advert, IBM emphasise that rates are subject to change and will vary according to configuration.
2. The assumptions we made have a big impact on the price. If we put smaller disks in the storage array, it would double the unit price. If we formatted it in RAID-1 mirrors, it would double it again.
3. Most importantly, the operating costs for running this are not included. Specifically: you would host and power it in your server room/data centre, and you would supply the labour needed to set up the backups, monitor that they run successfully, chase up failing backups, and check the backup server doesn't fill up. How much more could this cost? Again, your mileage will vary, but as a thought experiment: if 1 person costs US$50/hour and could manage up to 10 backup servers, then the additional cost would be around GBP 500 or USD 800 per server per month: driving the backup cost up to GBP 0.16 (USD 0.26) per Gbyte/month. I've no idea if these numbers are realistic - I'm just exploring how much your costs might change if you take into account the full operating costs.

As always - these are my personal thoughts and my current and previous employers may well see it differently.