# Backing up via cp causes blocks to be consumed on the source machine??



## MMacD (Aug 10, 2019)

I need to replace the re-badged LSI 9220-8i (probably really a Chinese counterfeit) that handles the zfs mirrors on my server-of-all-work since it has shed a port and a second one is flakey.  But I'm out of sata ports on the server, and so must do the pre-replace backup across my lan.  I'm using `cp` because I've never used `dump` and don't want to experiment on this task.

So I `nfs`-mounted the source filesystems and started the copy.  I'm watching progress using `df` and notice that the free block count is going down both on the destination drive AND on the source, which scared me.  Why would a copy be consuming blocks on the `nfs`-mounted source?


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## MMacD (Aug 10, 2019)

It would appear that the blocks are being used for buffering, though I would have thought buffers would be allocated in swap and not counted.  Apparently I happened to look at it while it was doing a long series of allocations without freeing anything up.  [sigh]   I'll purge the thread.  hmm...apparently I can't purge the thread.


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## SirDice (Aug 12, 2019)

MMacD said:


> I've never used  dump and don't want to experiment on this task.


You can't use dump(8) on ZFS, it's for UFS. For ZFS use `zfs send {...}` and `zfs receive {...}`.


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