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Funky disk magic - Ed's journal
sobrique
sobrique
Funky disk magic
I am here at work.
On a Bank Holiday.

And I'm doing a meta-device online expansion.

This is frightfully clever.
Basically, you take a 5 way striped mirrored system, and then add a mirrored volume to it.

Normally, this would effectively 'restructure' the disk, in such a way that the cylinders are no longer in the same layout, basically wiping your data.

The _clever_ bit here, is that I'm attaching BCV devices (EMC terminology. Stands for 'business continuance volume'. Basically just an 'extra' mirror). These BCVs will sync with the original volume, creating a track by track copy.
This copy remains available to the original host.

Then the 'original' 5x2 disk gets reassembled into a 6x2 disk structure. And then the tracks of the BCV get copied back in the same 'effective' layout as they were originally. (so striped linearly across 6 volumes rather than 5).

Which is a bit cool, because the symmetrix is hiding the fact that this is going on from the OS I'm doing it to. So I don't even have to umount the volume. Although I will have to do a growfs (diskpart extend to heretical windows users) once it's finished.

Always assuming this all works of course.
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Comments
jorune From: jorune Date: August 30th, 2004 09:27 am (UTC) (Link)
Love the last line, how many times have I heard techs carefully explain their actions and round it off with modest 'Always assuming this all works of course' for the non techs to go into headless chicken mode as someone suggests there's a risk!

sobrique From: sobrique Date: August 30th, 2004 09:37 am (UTC) (Link)
That's just revenge for large scale pointless meeting action. A subtle reminder that 'us techs' can destroy EVERYTHING! bwhahahaa.
xarrion From: xarrion Date: August 31st, 2004 05:26 am (UTC) (Link)
Unfortunately it also works as a subtle reminder of who to blame if it does... ;)
sobrique From: sobrique Date: August 31st, 2004 07:26 am (UTC) (Link)
You say that as though it makes the slightest difference in who the shit will land upon.
xarrion From: xarrion Date: August 31st, 2004 09:05 am (UTC) (Link)
Hmm, there is that... ;)
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