On Tue, November 15, 2011 17:05, Anatoly wrote:
> Good day,
>
> The speed of send/recv is around 30-60 MBytes/s for initial send and
> 17-25 MBytes/s for incremental. I have seen lots of setups with 1 disk
> to 100+ disks in pool. But the speed doesn't vary in any degree. As I
> understand 'zfs send' is a limiting factor. I did tests by sending to
> /dev/null. It worked out too slow and absolutely not scalable.
> None of cpu/memory/disk activity were in peak load, so there is of room
> for improvement.

What you're probably seeing with incremental sends is that the disks being
read are hitting their IOPS limits.  Zfs send does random reads all over
the place -- every block that's changed since the last incremental send is
read, in TXG order.  So that's essentially random reads all of the disk.

-- 
David Dyer-Bennet, d...@dd-b.net; http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

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