200 lines
6.9 KiB
Markdown
200 lines
6.9 KiB
Markdown
# The Story
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I was trying to migrate my data from one WD MyCloud EX 2 Ultra to another. This is my story of frustration, unanswered questions and a journey through bash + ssh.
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## TL;DR
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### Results
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As of now, transfer speeds are consistently around 20-25 MB/s with the bottleneck being target drive write speed. Looking for possible causes.
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### Takeaways
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* To check for network performance, start with `iperf` for throughput, then `ethtool` for hardware layer and then proceed with tuning if necessary
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* To check drive performance: `hdparm` and `dd` for read and write speeds, before checking transfer tools
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* In this case, there is no performance difference between `scp` and `rsync`, athough if I wanted to resume broken copy process, rsync provides option to skip existing files (as a workaround in scp we can force this by removing write persmissions to already existing files)
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## Initial conditions
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| Parameter | Source | Target |
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| Device | WD MyCloud EX2 Ultra | WD MyCloud EX2 Ultra |
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| Firmware | 2.31.204 | 2.31.204 |
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| Drives | 2 x 3 TB WDC WD30EFRX-68N32N0, FwRev=82.00A82 | 2 x 4 TB WDC WD40EFRX-68N32N0, FwRev=82.00A82 |
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| Raid | Raid-1 | Raid-0 |
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| Encrypted | No | Yes |
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| IP address | 192.168.1.54 | 192.168.1.53 |
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Connected using Cat 5E cables via TP-Link TL-SG108 Gigabit switch.
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## Testing
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First, I enabled ssh access in both NASes via web-ui:
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```Settings > Network > SSH```
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Default user for WD Mycloud EX2 Ultra is `sshd` so to connect to NAS I used command:
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```ssh sshd@192.168.1.53```
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To avoid multiple data transfers I logged into target ssh and tried to copy from source using `scp` command:
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```
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scp -rp sshd@192.168.1.54:/mnt/HD/HD_a2/Marcin /mnt/HD/HD_a2/
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```
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However, the transfer speed oscillated between 20-25 MB/s. This is way below expected 70 MB/s.
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First I checked if network cards indeed connected using 1000 Mbps full-duplex using `ethtool`:
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```
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# ethtool egiga0
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Settings for egiga0:
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Supported ports: [ TP MII ]
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Supported link modes: 10baseT/Half 10baseT/Full
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100baseT/Half 100baseT/Full
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1000baseT/Full
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Supported pause frame use: No
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Supports auto-negotiation: Yes
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Advertised link modes: 10baseT/Half 10baseT/Full
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100baseT/Half 100baseT/Full
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1000baseT/Half 1000baseT/Full
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Advertised pause frame use: No
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Advertised auto-negotiation: No
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Link partner advertised link modes: 10baseT/Half 10baseT/Full
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100baseT/Half 100baseT/Full
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1000baseT/Full
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Link partner advertised pause frame use: No
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Link partner advertised auto-negotiation: Yes
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Speed: 1000Mb/s
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Duplex: Full
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Port: MII
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PHYAD: 0
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Transceiver: internal
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Auto-negotiation: on
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Link detected: yes
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```
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And that the IO and CPU are not saturated (those were already visible with web-ui, but I used `iostat`):
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```
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# iostat
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Linux 3.10.39 (KlinkierChmurka) 05/05/20 _armv7l_ (2 CPU)
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avg-cpu: %user %nice %system %iowait %steal %idle
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29.23 6.16 28.23 1.36 0.00 35.02
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```
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```
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# iostat -dx /dev/sda 5
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Linux 3.10.39 (KlinkierChmurka) 05/05/20 _armv7l_ (2 CPU)
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Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
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sda 0.55 5.39 4.01 95.83 212.68 10755.40 219.70 0.45 4.53 4.82 4.52 1.19 11.90
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```
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I then checked if they are properly routing through the switch with `traceroute`:
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```
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# traceroute 192.168.1.54
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traceroute to 192.168.1.54 (192.168.1.54), 30 hops max, 38 byte packets
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1 192.168.1.54 (192.168.1.54) 0.428 ms 0.428 ms 0.391 ms
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```
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Then I enabled jumbo frames in the web-ui and verified they are working using `ping`:
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```
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# ping -s 8972 192.168.1.54
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PING 192.168.1.54 (192.168.1.54): 8972 data bytes
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8980 bytes from 192.168.1.54: seq=0 ttl=64 time=0.898 ms
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8980 bytes from 192.168.1.54: seq=1 ttl=64 time=2.904 ms
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8980 bytes from 192.168.1.54: seq=2 ttl=64 time=0.786 ms
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```
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To do performance test I stopped the scp pressing `Ctrl-Z` (that would allow me to resume it later using `bg` of `fg`) and ran a network throughput test using `iperf`:
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Source:
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```
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# iperf -s
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------------------------------------------------------------
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Server listening on TCP port 5001
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TCP window size: 85.3 KByte (default)
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------------------------------------------------------------
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[ 4] local 192.168.1.53 port 5001 connected with 192.168.1.54 port 41261
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[ ID] Interval Transfer Bandwidth
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[ 4] 0.0-10.0 sec 1.16 GBytes 991 Mbits/sec
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```
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Target:
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```
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# iperf -c 192.168.1.53
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------------------------------------------------------------
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Client connecting to 192.168.1.53, TCP port 5001
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TCP window size: 93.3 KByte (default)
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------------------------------------------------------------
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[ 3] local 192.168.1.54 port 41261 connected with 192.168.1.53 port 5001
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[ ID] Interval Transfer Bandwidth
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[ 3] 0.0-10.0 sec 1.16 GBytes 992 Mbits/sec
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```
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This would rule out the network bottleneck. I decided to perform test on one large file using both `scp` and `rsync`, which can sometimes outperform `scp`.
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```
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# cd /mnt/HD/HD_a2/Marcin/
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# dd if=/dev/zero of=1GB_TEST_FILE bs=1G count=1
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1+0 records in
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1+0 records out
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1073741824 bytes (1.0GB) copied, 37.631790 seconds, 27.2MB/s
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```
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Starting with `scp`. Speed is consistent with what I obserwe with real data:
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```
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# scp -rp sshd@192.168.1.54:/mnt/HD/HD_a2/Marcin/1GB_TEST_FILE /mnt/HD/HD_a2/Marcin/1GB_TEST_FILE
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sshd@192.168.1.54's password:
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1GB_TEST_FILE 100% 1024MB 22.2MB/s 00:46
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```
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Now `rsync`. Unfortunately, no improvement there:
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```
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# rsync -a sshd@192.168.1.54:/mnt/HD/HD_a2/Marcin/1GB_TEST_FILE /mnt/HD/HD_a2/Marcin/1GB_TEST_FILE --progress
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sshd@192.168.1.54's password:
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receiving incremental file list
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1GB_TEST_FILE
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1073741824 100% 21.57MB/s 0:00:47 (xfer#1, to-check=0/1)
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sent 30 bytes received 1073872980 bytes 20851903.11 bytes/sec
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total size is 1073741824 speedup is 1.00
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```
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But wait, didn't the `dd` created the file on source NAS with speed around 27 MB/s? Time to bench the drives.
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Source read speed:
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```
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# hdparm -t /dev/sda
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/dev/sda:
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Timing buffered disk reads: 538 MB in 3.01 seconds = 178.73 MB/sec
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```
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Target write speed:
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```
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# dd if=/dev/zero of=1GB_TEST_FILE bs=1G count=1
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1+0 records in
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1+0 records out
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1073741824 bytes (1.0GB) copied, 41.367580 seconds, 24.8MB/s
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```
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Ok, so it would seem drive writing speed would be at fault. But why? SMB transfers to the drive are faster, 50-70 MB/s, close to advertised. And it would seem that I am not the only one with such problem (SCP slow, SMB fast):
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* https://forums.freebsd.org/threads/slow-nfs-smb-afp-but-fast-scp-read-performance.68077/#post-410296
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However, the benchmarks around web seem to find scp an rsync much faster than SMB:
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* https://squarism.com/2010/02/12/scp-vs-rsync-vs-smb-vs-ftp/
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Having depleted my theories I decided to ask WD community:
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https://community.wd.com/t/wd-mycloud-ex2-ultra-2x4tb-slow-write-speeds-over-ssh/250988
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