volume expansion time vs % of volume filled?

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xoda
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volume expansion time vs % of volume filled?

Postby xoda » Fri Feb 17, 2017 5:16 am

Assuming the disk size and number of disks are the same, does how much the volume is filled with data impact its expansion/rebuild time?

For example, if I have a a volume with two 10TB hdds in SHR. I want to add another 10TB hdd. Does the expansion time matter if I the volume is 15% filled vs if it's 50% filled? If there's an impact, is it linear - i.e. a 50% filled volume taking twice as long as a 25% filled volume?
drabisan
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Re: volume expansion time vs % of volume filled?

Postby drabisan » Fri Feb 17, 2017 3:49 pm

Much more complicated than just copying data!
Health check is directly connected to the size of the drive and the speed of the drive. Assuming same speed, a 10T will take double the time of 5T.
Rebuilding the actual data structure if a complex process. It reads all data, it calculates some checksums, it copy some data and it deletes it from the old drive, it writes the checksums according to the volume type, it "syncs" some sectors and the list can continue.

A quick conclusion - the amount of data doesn't impact significantly the process of migrating from 2 drives to 3 drives. But you need to make sure you are not with a full volume! Actually you should not ever be above 90% not to run into other problems.
xoda
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Re: volume expansion time vs % of volume filled?

Postby xoda » Fri Feb 17, 2017 7:17 pm

Thanks for that very detailed explanation!

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