Archive for April, 2010

Snapshot – delta file doom!

Thursday, April 22nd, 2010

There was a pretty decent argument happening at work the other day regarding how vmware handled snapshot files. We all knew and understood delta files were created on a hard disk basis and understood these delta files were the secret to the snapshot success.

Some people were convinced the delta files acted as a transaction log (similar to an SQL transaction log) that would capture and log any changes made to the base disk file. In this instance the delta file could grow without a limit – any number of changes could be applied to the base disk that would cause the delta ‘transaction log’ to be updated. If this were the case, the size of the delta file could easily exceed the size of the original vmdk.

This was the issue at question – I was adamant the delta file could not exceed the size of the vmdk that was being ‘snapped’. I can’t recall where I got this idea – but I was adamant. Must have been a hang over from the ESX 3.5 Fast track course I sat a while back.

I presented my case that the delta file was simply a block level copy of any changes that had been made – as in changes were made to the delta file instead of the base vmdk. Then when the snapshot was merged (deleted) these changes were just applied to the base vmdk. In this scenario – a delta can never exceed the size of the vmdk. As there is a finite amount of data defined.

Turned out to be an interesting conversation and I started to lose faith in my belief – so I did some googling around and found 2 decent articles:

This one provides some great information on how the delta file is created and written to. This cemented my ideas of how the delta works and I knew on the right track.

This one is less technical but answered the question none the less.

I’d recommend the first link for anyone that works with snapshots on a daily basis like we do – it really gives a good foundation to the underlying tech.

Get you inner nerd on – clothes style!

Thursday, April 22nd, 2010

During my regular visit to the intertubes (aka pipes) – I come across some awesome clothing. I always want it. It always costs money and it rarely ends up looking as cool when it arrives.

The latest:

Ok – so people might not get these. The first hoodie is a mass effect reference. Second is a tron nod! IT GLOWS! COOLS!

Stargate: Universe

Friday, April 2nd, 2010

I am really feeling this show lately. I am old school Stargate. Not one of my proudest boasts – but I’ve been hooked since the first movie. Watching all of SG1 and then even following the foray in to Atlantis (which was ok dammit!) and then even hung around when the whole SG1 team changed…

Then it all sorta closed up. A few TV movie type things were released (see Ark of Truth etc) but they were just to close up the plot lines. I went off and pursued other interests. Battlestar Gallactica scratched that itch for a while – but at times it was trying.

Imagine my joy when SGU was released and billed as a cross between Atlantis and BSG. All the good bits of Stargate (aliens, space… and errr Stargates!) crossed with the adult concepts of BSG. Win.

Half way through season one and its pretty decent. I’d recommend it to anyone looking for something after BSG has closed up (along with Caprica – post to come). Good character to development. Decent plot line with a heap of space to grow – pretty much the way it is structured allows for it to go in any direction without an end in sight. People are trapped on a spaceship here!

The last ep I watched (ep 11 – Space) introduced some what of an ‘enemy’ alien race that I imagine will keep coming up in the series. Akin to the ‘wraith’ in Atlantis or the ‘ghould’ in SG1.

If you haven’t had a chance to hit it up and you like the SciFi (ScyFy – OH GOD NO!). Get in there and have a watch.

post script: It pains me to say – but there are inconsistencies. Jemma says I am too picky about these things…. but really. On a spaceship. Trapped. In space. Alone. Where do people get new/clean clothes? I guess there could be some form of alien laundromat on ‘destiny’ … ok what about ammo then? surely they are going to run out.

MOVING ON! or else I will dwell for evar!