I want you to see my storage automagically

Jan 22, 2012 / 0 comments

For my day job I build storage systems. A lot of what I do at present involves caring a lot about how different OSes deal with things like new LUNs being presented from a SCSI target, or errors along a subset of the available paths to a device.

It will come as no surprise to you to discover that they all suck (for values of all equal to Linux, Solaris, Windows and VMWare). New LUNs are particularly annoying. I’m in the situation that creation and removal of a LUN is exceptionally easy.

Hmmm. Maybe I need to back up here a bit first. SCSI has the concept of a target (think, device, eg hard drive). Each target can present multiple logical units. Each of these is assigned a number - a Logical Unit Number. Most devices (a hard drive, or a CDROM drive) will present a single LUN. A storage array will tend to present multiple LUNs; one for each volume that is exported to the host. At the host level each LUN really just looks like a separate device (for Linux /dev/sda and /dev/sdb may well be separate LUNs on the same array, rather than 2 separate arrays/hard drives, for example. At the block device level you don’t care about the difference usually).

Anyway. For various reasons I end up adding and removing LUNs quite often. And there are ways for the array to indicate that this has happened to the host (the UNIT ATTENTION/REPORT LUNS DATA CHANGED check condition seems to be favoured these days, as a complete Fibre Channel LIP can be disruptive). What I’d like to happen in that case is the host to pick up the check condition and drop and/or add the devices that have changed. Instead everything wants a manual rescan. rescan-scsi-bus tends to be simplest for Linux. Windows wants a manual refresh in Disk Administrator. VMWare a “Rescan HBAs” from vSphere. Solaris a “devfsadm -C” and possibly a “cfgadm -al” first. And all of these can be temperamental about picking up the changes.

We’ve done a lot about hotplug for the desktop user experience, without doing the same level for the server experience. I appreciate that there are situations that you don’t want your server to reconfigure things without being told to, but the current situation can be detrimental (for example Linux multipathing will hold a device open even after it’s disappeared and is returning an “INVALID LUN” response; it would be much better if it could cleanly close that device and wait for it to return). Storage is capable of being much more than just a single block device these days, and it’s a shame that nothing seems to deal fully with that fact.

(Yes, yes, I should write and submit patches, but I appreciate that there’s not always a simple answer, nor necessarily an answer that works for all situations automatically. Plus, y’know, not enough hours in the day and I hope you all appreciate I’ve taken a break from watching BSG to write this.)

Totally divorced

Jan 22, 2012 / 0 comments

I got divorced earlier this month; the decree absolute arrived in the post last weekend. I’m hoping this isn’t news to anyone who knows me well, and I only really mention it here as an endpoint given that I blogged about the wedding itself.

All I need is a large enough white wall

Nov 26, 2011 / 0 comments

I think I’m currently supposed to be out buying a TV at the moment. Or something else expensive. Instead I’m lying on the sofa listening to Whale and drinking tea. That’s much better in my opinion, but it reminded me that I hadn’t mentioned that I bought a projector.

I had the loan of a projector for a while when I was in Belfast. It was a huge thing that made a lot of noise, but was pretty cool for watching films with. When I moved to the US I decided not to bother with a TV to start with - using my laptop did just fine for most things. Except films. They really benefit from a bigger screen. Especially if you want to watch them with someone else. So I started looking at pico projectors, because I wanted something small and cute that I could throw in a bag with my tiny laptop. At the time the best the pico projectors could do was 840x480, which I felt wasn’t really that great. However back in January TI announced their DLP Pico HD chipset, offering a resolution 1280x800.

I kept a look out for projectors using this to appear, and eventually, in July, Amazon claimed to have availability of the Vivtek Qumi. So I bought one. And I’m very happy with it. I’m not a heavy user, and there are some niggles, but it’s small and does exactly what I want. In low light conditions it’ll happily throw an image all the way across the room, which is more than it’s rated at. There’s a mini-HDMI connector on the back, so it’s a doddle to plug it into my laptop using the supplied HDMI to mini-HDMI cable. The laptop auto-detects the device and extends the desktop appropriate, as you’d expect.

It’ll also do media playback itself - there’s a USB host port and a micro SD slot on the back. This works ok, and the included remote means you can easily set the projector somewhere above your head and still be able to easily control it. Unfortunately the built in speakers are fairly useless. There’s a 3.5mm socket for external speakers, but having to plug something else in detracts from the convenience factor of the built-in media player. Also my unit had the power switch installed upside down (the little red line indicating the power is on actually shows up when it’s off), but that’s the only complaint I’ve got about the build quality. There’s a little neoprene case to store the thing in as well.

So, er, yeah. I think I can continue to make do without a normal TV for a while longer and avoid the nightmare that I suspect are the shops on Black Friday.

The cost of progress

Nov 8, 2011 / 0 comments

You should probably ignore this post. I’m just venting. I’ll be better after a nice cup of tea.

Things that are causing me to fume about the fact Gnome Shell just hit Debian/Testing:

  • Spacefun came back. Even on GDM3. Just fucking die already.
  • I had to reboot to get bluetooth working again.
  • /desktop/gnome/shell/windows/workspaces_only_on_primary set by default? SRSLY?
  • It failed to carry over my previous monitor settings.
  • I’m pretty sure I don’t have a latent desire for a machine running OS X, whatever the GNOME devs might think.
  • How many mouse clicks to get to the list of applications?
  • Er, why have you changed my default apps? (Why is clicking a link in a terminal opening Epiphany rather than a new tab in Iceweasel?)

I update my testing boxes (work + home laptops) almost every day. It rarely breaks, and certainly when it does I accept that’s what I get for doing rolling upgrades. I can’t remember the last time I did an upgrade that actually made me angry.

Also I suspect this thing is going to have a complete fit on my binary nVidia/hacked up DisplayLink configuration at work (the DisplayLink side refuses to do 3D for starters). Perhaps better not to upgrade there until I have a sufficient block of free time.

Maybe it’s time to go back to evilwm. I only stopped because I wanted a dock for wifi/bluetooth etc applets on my laptop that didn’t get hidden when I fullscreened things. Implementing _NET_WM_STRUT might make that doable…

(I’m sure some of this is just dealing with the change but it’s a bit bloody difficult to deal with a complete change in user interface that hasn’t even managed to carry across settings from the old one.)

Thanks for the offer, but...

Oct 5, 2011 / 0 comments

I was due for another Google interview mail it seems. I have to say I wasn’t expecting it, but this week I had a follow up to my polite mail from 6 months ago that said “No thanks, I’m not looking” asking if it was still the case.

Normally I welcome this little bit of ego stroking; it’s always nice to be wanted. Except that’s not really the case, is it? It’s an invitation to interview for something, not any indication that you’ve done more than tick some initial boxes. Google mails inevitably ask me if I’d like to work in SRE. It’s always SRE. No one ever emails and asks if I want to work on self-replicating nanobots that will roam Mars searching for the perfect spot to build a beach house.

And that’s where things fall down. If someone currently has a job, then emailing them out of the blue to ask if they want to come and interview for something vague is hoping that they’re either looking, and just haven’t come to you yet, or not looking but unhappy enough with their current role that all they needed to start was an email asking them to submit a recent CV.

For the former, if you’re Google, do you really think that person doesn’t know where to find you? For the latter, you’re being quite presumptuous, aren’t you? The act of updating my CV my be some effort (actually it’s usually not, because the stuff that’s not on it is the stuff I can’t talk about because it’s not released yet, or stuff that’s specific and thus wouldn’t go on a CV for a vague job spec). Even if it’s not the act of interviewing is potentially a waste of time for both of us, if the role isn’t clear.

One argument used is that people will be placed according to the skills they show during the interview process. That’s fine from the employers point of view, but if you’re actively trying to get some interest from people who are gainfully employed you really need to grab their attention somehow. I can’t remember the last time I had an unsolicited email interview offer that actually wowed me, or indeed even showed more than a passing sign of tailoring a spec to my profile.

When I was running Black Cat I made a point of always replying to unsolicited CVs. How polite I was depended on how the covering emails were worded (a Word document with nothing else was likely to get short shrift, something well targeted in a Linux friendly format would normally get some comment about how we weren’t hiring and were unlikely to be, but if that changed it would be mentioned on the website), but I felt people deserved a reply - I have been disappointed by not receiving responses myself to what I considered well targeted job inquiries.

So far I’ve so far taken the same approach with mails from corporate recruiters (less so with recruiters that are associated with recruitment firms, rather than directly with the companies they are hiring for), but I’m starting to feel like changing that stance. Candidates are told to tailor CVs to the role being applied for, provide a decent cover letter, and in general make companies want to talk to them. Companies who are sending out recruitment emails should be held to the same standard. Even assuming you do a basic phone screen first, I can probably expect to need to take a day off work assuming that goes well. You need to convince me I can justify that before I’m going to feel like engaging at all.

(And if I’m honest, based on what I’ve seen so far, it’s unlikely to happen. All of the things I’ve considered have come from conversations with people I know directly about companies they own or work for, never some random contact via email. I try hard not to think of recruitment mail as spam, but I can how that line of thought follows through.)

I should apologize to Google here. They got mentioned as an example, but I don’t think they’re particularly bad. I did interview with them at one point, and made the decision not to continue that process after deciding a different, more certain, path was better for me. So I’ve displayed interest. And in response to my reply today of “I know where to find you, so please assume I’ll do so if I change my mind.” they’ve said they’ll make a note on their records.

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