Rich - ZFS Followup

This is a followup to your response to my question in Episode 141@1:34:35

    I have since upgraded FreeNAS 9.3 to 9.10.

    The iTunes music library is not contained within the VDI file, the VM connects to SAMBA on the FreeNAS where the music repository is located on a dataset. I'm not that bad of a Noob. LOL.   The VDI file is large only to allow room for future upgrades.  (My original VDI size was not large enough to allow Windows XP to be upgraded to Windows 7 so I made the VDI file size large enough that I don't have to worry about future upgrades should they be needed).  This iTunes VM is only occasionally used for iOS upgrades and backups, I'm not a fan of the iCloud and keep it disabled.

    You suggested - Disable rsync compression - this is disabled by default and requires "-z" to enable, I do not enable this.

    You suggested - Use "dd" as a test, I assume you meant from linux desktop, mount nfs volume to where vdi file is and then run:

$ dd if=iTunesLibraryDynamic.vdi of=/dev/null bs=1MB
1622+0 records in
1621+0 records out
1621000000 bytes (1.6 GB, 1.5 GiB) copied, 26.3588 s, 61.5 MB/s

I ran it a few times for different time duration, each result was very close to above such as:

21444+0 records in
21443+0 records out
21443000000 bytes (21 GB, 20 GiB) copied, 335.384 s, 63.9 MB/s

I ran this one on the FreeNas directly (513MB/sec ?? wow)

dd if=iTunesLibraryDynamic.vdi of=/dev/null bs=1M
23747+0 records in
23747+0 records out
24900534272 bytes transferred in 48.507604 secs (513332594 bytes/sec)

    You suggested - rsync "sparse" which looks very handy for the 1st time you run a backup via rsync, but subsequent backups look like they should use "--inplace" instead (only blocks which have changed).  To test the "--inplace" I wanted to make sure enough blocks had been updated for a typical use case, so for each VM I updated guest additions and ran windows updater to apply patches, etc.

Results:

main/vm_storage/QuickBooksPro/QuickBooksPro.vdi
 49,358,569,472 100%   34.35MB/s    0:22:50 (xfr#51, to-chk=15/62084)

main/vm_storage/iTunesLibrary/iTunesLibraryDynamic.vdi
 72,868,691,968 100%   41.68MB/s    0:27:47 (xfr#58, to-chk=6/62084)

That is much improved over the 11MB/sec to 13MB/sec I was getting but still very low for gigabit Ethernet.

Q: In my research I saw recommendations to use much weaker encryption with Rsync and SSH such as ArcFour, but you did not make any comments related to encryption and throughput.  Even over my own network, I think I would rather wait a little longer then to allow weaker encryption, but I'm open to suggestions.  The debug on my ssh connection reports:

debug1: kex: server->client cipher: aes192-ctr MAC: hmac-sha2-256 compression: none
debug1: kex: client->server cipher: aes192-ctr MAC: hmac-sha2-256 compression: none

Output of TOP while ssh/rsync is in progress:

last pid:  1924;  load averages:  1.34,  1.07,  0.67                                                        up 3+21:17:17  20:54:05
79 processes:  2 running, 77 sleeping
CPU: 13.2% user,  0.1% nice,  6.6% system,  0.3% interrupt, 79.7% idle
Mem: 12M Active, 1408M Inact, 29G Wired, 286M Free
ARC: 27G Total, 26G MFU, 384M MRU, 6560K Anon, 126M Header, 584M Other
Swap: 8192M Total, 8192M Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU COMMAND
 1299 root          1  89    0 56816K  7740K RUN     3   4:48  55.86% ssh
 1298 root          1  36    0 16900K  3096K select  0   2:10  25.20% rsync
 2881 root         12  21    0   235M 29660K nanslp  2  15:26   0.00% collectd

Thanks for any additional suggestions you may have.

-Rich