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Initial Sync took 14 hours?

sg86
Aspirant

Initial Sync took 14 hours?

I've just put in 4 x 4TB 00'ed drives and it's taking 14hours to "sync", well nothing should be syncing lets be clear, why is it taking so long to initlaise a RAID5 array?

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StephenB
Guru

Re: Initial Sync took 14 hours?


@sg86 wrote:

I've just put in 4 x 4TB 00'ed drives and it's taking 14hours to "sync", well nothing should be syncing lets be clear, why is it taking so long to initlaise a RAID5 array?


RAID creates a virtual disk (block storage); the file system is built on top of that.  So creating/syncing the RAID array takes the same amount of time when the file system is empty as it does when it is full. 

 

Therefore, 16 TB of disk I/O is needed to sync the array (even with no data) - 12 TB to read the data blocks, and 4 TB to write the parity blocks.  That takes a while.  If it takes 14 hours, it will be processing ~300 MB/sec.

 

This could be faster if the system assumed the disks were zeroed.  But it doesn't make any assumptions about what's on the drives.

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