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How fast does a data device drain from a pool ?
I know this is one of those questions where "It depends ..." :-) But does anyone have any rough figures ?
I've a pool that needs a number of data devices from a disk group drained out of it, for change control etc I need to roughly estimate how long it would take.
It's a VMAX, 4 engines, and the data devices are from 15k FC and 7.2K SATA disk groups.
I just need an guess answer like "a 200GB data device will take xxxx hours to drain when the VMAX BE utilisation is xx%"
(I could make up my own numbers but would like something based on better theory than reading tea leaves :-)
Zikas
278 Posts
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February 15th, 2013 13:00
The procedure is the following:
Before removing a data device from a pool, the device must be disabled.Disabling a data device changes its state from Enabled to Draining.
The concept of device draining is common to all ytpes (data and snap pools).
When a device enters a draining state, used tracks on that device are copied to the remaining, enabled devices in the pool. Therefore data devices can be removed from a pool and repurposed without having to unbind thin devices that may have allocated extends associated with the data device.
I have performed a drain on three data devices the same time which were created on FC disks and they were around 110000 cyls each.
Were used around 55% and the drain took around one hour, on working hour (i mean 9 to 5) where the VMAX was busy and if i remember well the VMAX has 5 engines.
Zikas
278 Posts
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February 15th, 2013 13:00
Also the time that it will take to drain a data device is how much that data device full is?
Probably if the Variable Rebalance is set to 1% the data device are balanced full but has to do how much full are the data device.
Zikas
278 Posts
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February 15th, 2013 13:00
Hi Mark,
what is your microcode? 5874, 5875, or 5876?
I have read that in 5876 the drain is much more quick than in 5875.
Also what kind of type is the VMAX? 20K or 40K?