On 2/16/2017 9:18 PM, Keith Keller wrote:
On 2017-02-15, John R Pierce<pie...@hogranch.com>  wrote:
On 2/14/2017 4:48 PM,tdu...@palmettoshopper.com  wrote:

3 - Can additional drive(s) be added later with a changein RAID level
without current data loss?
Only some systems support that sort of restriping, and its a dangerous
activity (if the power fails or system crashes midway through the
restriping operation, its probably not restartable, you quite likely
will lose the whole volume)
Doesn't mdraid support changing RAID levels?  I think it will even do it
reasonably safely (though still better not to have a power failure!).  I
have a vague memory of adding a drive to a RAID5 and converting it to a
RAID6 but I could be misremembering.

any such operation requires the entire raid to be re-slivered, stripe by stripe, as ALL the data moves around. on a large raid made from multi-terabyte drives, this would take DAYS.


--
john r pierce, recycling bits in santa cruz

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