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Nexus7 tablet power issues resolved

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Last year while attending Gestalt IT’s SFD#2 I was lucky enough to be given a Nexus7 tablet by Asigra. For the last year it’s served me well but about a month ago I started to have issues whereby it wouldn’t charge properly and even leaving it plugged in overnight didn’t charge it to 100%. I ignored it for a while until it finally died completely and wouldn’t charge at all.

At that point I did what everyone does and resorted to Google. Power issues on the Nexus7 tablets (both 2012 & 2013 models) are a pretty common issue and after I ran through the standard ‘my tablet won’t charge’ steps  I rang Google to get a replacement as it was only 10 months old. They advised that I needed the email address used to buy the device if I wanted to claim on the warranty. This was complex as it was given to me by a US based company and futhermore they said even if I could find the contact I’d have to return the tablet to the US and pay for shipping both ways. For a tablet that cost £150 new and which has already been superseded that hardly seemed worth it.

Faced with a dead tablet I figured I had nothing to lose so I thought I’d try replacing the battery and hope that was the fault. It turns out it’s pretty easy to do (unlike Apple kit which is nigh on impossible to fix) and batteries can be found cheap on Ebay (often from tablets with broken screens). Luckily for me I didn’t get as far as replacing it – I simply unplugged the battery and reconnected it as firmly as I could and hey presto, I was back in business. The tablet started charging again and I’ve since found that it charges much quicker (<4hrs from 0% to 100%) and even seems to last longer in standby. Maybe my battery has always had a slightly dodgy connector – it’s cheaper than Apple kit for a reason I suspect!

Motto of the day – give it a try and you might get lucky! Be aware that taking off the cover may invalidate your warranty so use at your own risk!

Is the HP power setting impacting your performance?

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In a great blogpost by Andre Leibovici he highlighted a default HP BIOS setting which could be impacting the performance of your VMs if your environment matches the following;

  • low physical CPU utilisation
  • higher than expected CPU %Ready times

Julian Wood has also blogged about this issue (Your HP blades may be underperforming) but neither go into too much detail about the fix. Having investigated I thought I’d record it here for others convenience.

To check for these symptoms you could use the VI client, ESXTOP in batch mode combined with the batch processing scripts in the vMA to capture pCPU statistics from a group of servers, or PowerCLI -whichever suits your skillset.

We run HP C-class blades and after checking the VMware knowledgebase article KB1018206 and a sample of our BIOS settings we found that it applied to us too – not surprising as we don’t modify the BIOS defaults during provisioning.

Using a mixture of ESXTOP and vCenter’s performance charts I was able to confirm that the %CPU Ready was hovering around the 4% mark even when the physical host was using less than 15% pCPU. After changing the power setting the same VMs (under a similar load) dropped to under 1% CPU Ready (the change was made at 17:00 if you look at the graph).
Not necessarily a show stopper but definitely an improvement

For my infrastructure (with around 160 physical blades) changing them all was a time consuming process (and could potentially be disruptive depending on whether your ESX/i hosts are all clustered).

You can check the current power management setting in various ways;

  • in the BIOS settings (slow and potentially disruptive)
  • via the ILO (under Power Management, Power settings) or via the ILO CLI
  • in the VI client. If the underlying BIOS is set to Dynamic Power Savings it’ll show as ‘Not Supported’ . ie the hardware is controlling power management. Where to check depends on your version of ESX (or ESXi);
    • For a 40 host go to Configuration -> Processors and look at the Power Management settings.
    • For a 4.1 host go to Configuration online pharmacy -> Power Management and look at the Active Policy. You can also configure it using the Properties button.
  • You can also use PowerCLI (ESX4 only) by querying the host’s Advanced setting ‘Power.cpupolicy’
    get-vmhost myhost | get-vmhostAdvancedConfiguration -name Power.cpupolicy
Changing power saving via the ILO

Continue reading Is the HP power setting impacting your performance?

I’m on TV, TV Soup to be precise!

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Earlier today I found myself on the vSoup podcast with @eczerwin, @chrisdearden, and @hobbel (though in potato form!) from vSoup. We’d been chatting in the bloggers lounge at VMworld Copenhagen about the sessions, labs etc and they kindly invited me to chat with them live on TV. You can watch the live stream although I can’t promise you’ll learn anything! We discuss the hands on labs and where they might go next along with reasons you might want to be at VMworld.

Welcome to yet another technology blog…

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With the upcoming VMworld conferences in San Francisco and Copenhagen I figured now was a good time to have a blog handy in case I wanted somewhere to air my thoughts and hopefully get some community feedback. The techie in me also wants to understand the technology behind blogs be it WordPress, widgets, CSS, or reverse proxying and as always the only way to learn is to jump in and get your hands dirty.

A post by VMware’s John Troyer a few months ago discussed what distinguished the people who were awarded the vExperts accolade. I’ve no illusions about becoming a vExpert or making the top 100 blogs – I support the internal infrastructure for a not-for-profit company and consequentyly don’t have the exposure that some have to new technologies and leading edge implementations. In my own words I’m a lurker – I love soaking up knowledge and I enjoy mentoring people but I don’t always think what I have to say is of interest to others (whether it is or not). I’m very happy that some people are so inclined however or I wouldn’t have anywhere to soak up knowledge from!

There are two points from John’s post which resonate with me. Invest a slice of time in yourself, and break out of your silo – sounds like good advice to me.