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ZFS Fragmentation question

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Mr_N

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Would it make any difference if I deleted the data I'm going to replace before extending my pool with 2nd vdev or after?
 

mav@

iXsystems
iXsystems
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Addition of new vdev does not move any data to it by itself. So it should not make difference whether you delete anything before the addition or after. New writes on the other hand should matter -- writes done after new vdev added for significant part will go to new vdev and will be written there with minimal fragmentation.
 

Mr_N

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so it isn't an equal striping across vdevs if one is already ~40-50% full?
 

mav@

iXsystems
iXsystems
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ZFS stripes data between vdevs based on their write performance. Old full and probably fragmented vdev will likely be slower then empty new one, so it should receives less new writes.
 

Mr_N

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ahh ok
 
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