I've looked on some of the Synlogoy forums and it does appear some people are complaining about performance of the GUI.
I just copied over a 20GB file in about 7 mins so the disk performance seems ok.
Here's the serial output -
[H[J[1;1H[?25l[m[H[J[1;1H[2;20HGNU GRUB version 2.02~beta2-36ubuntu3.14
[m[4;2H+----------------------------------------------------------------------------+[5;2H|[5;79H|[6;2H|[6;79H|[7;2H|[7;79H|[8;2H|[8;79H|[9;2H|[9;79H|[10;2H|[10;79H|[11;2H|[11;79H|[12;2H|[12;79H|[13;2H|[13;79H|[14;2H|[14;79H|[15;2H|[15;79H|[16;2H|[16;79H|[17;2H+----------------------------------------------------------------------------+[m[18;2H[19;2H[m Use the ^ and v keys to select which entry is highlighted.
Press enter to boot the selected OS, `e' to edit the commands
before booting or `c' for a command-line. [5;80H [m[5;3H DS3615xs 6.2 Baremetal with Jun's Mod v1.03b [m[5;78H[m[m[6;3H DS3615xs 6.2 Baremetal with Jun's Mod v1.03b Reinstall [m[6;78H[m[7m[7;3H*DS3615xs 6.2 VMWare/ESXI with Jun's Mod v1.03b [m[7;78H[m[m[8;3H [m[8;78H[m[m[9;3H [m[9;78H[m[m[10;3H [m[10;78H[m[m[11;3H [m[11;78H[m[m[12;3H [m[12;78H[m[m[13;3H [m[13;78H[m[m[14;3H [m[14;78H[m[m[15;3H [m[15;78H[m[m[16;3H [m[16;78H[m[16;80H [7;78H[22;1H The highlighted entry will be executed automatically in 1s. [7;78H[22;1H The highlighted entry will be executed automatically in 0s. [7;78H[?25h[H[J[1;1H[H[J[1;1H[H[J[1;1H[H[J[1;1Hpatching file etc/rc
patching file etc/synoinfo.conf
Hunk #1 FAILED at 291.
1 out of 1 hunk FAILED -- saving rejects to file etc/synoinfo.conf.rej
patching file linuxrc.syno
Hunk #3 succeeded at 552 (offset 1 line).
patching file usr/sbin/init.post
cat: can't open '/etc/synoinfo_override.conf': No such file or directory
START /linuxrc.syno
Insert basic USB modules...
:: Loading module usb-common ... [ OK ]
:: Loading module usbcore ... [ OK ]
:: Loading module ehci-hcd ... [ OK ]
:: Loading module ehci-pci ... [ OK ]
:: Loading module ohci-hcd ... [ OK ]
:: Loading module uhci-hcd ... [ OK ]
:: Loading module xhci-hcd ... [ OK ]
:: Loading module usb-storage ... [ OK ]
:: Loading module BusLogic ... [ OK ]
:: Loading module vmw_pvscsi ... [ OK ]
:: Loading module megaraid_mm ... [ OK ]
:: Loading module megaraid_mbox ... [ OK ]
:: Loading module megaraid ... [ OK ]
:: Loading module scsi_transport_spi ... [ OK ]
:: Loading module mptbase ... [ OK ]
:: Loading module mptscsih ... [ OK ]
:: Loading module mptspi ... [ OK ]
:: Loading module mptsas ... [ OK ]
:: Loading module mptctl ... [ OK ]
:: Loading module megaraid_sas ... [ OK ]
:: Loading module mpt2sas ... [ OK ]
:: Loading module mpt3sas ... [ OK ]
Insert net driver(Mindspeed only)...
Starting /usr/syno/bin/synocfgen...
/usr/syno/bin/synocfgen returns 0
All disk ready or timeout execeed
[ 1.900290] md: invalid raid superblock magic on sdb5
Partition Version=7
/sbin/e2fsck exists, checking /dev/md0...
/sbin/e2fsck -pvf returns 0
Mounting /dev/md0 /tmpRoot
------------upgrade
Begin upgrade procedure
No upgrade file exists
End upgrade procedure
============upgrade
Wait 2 seconds for synology manufactory device
Sun Nov 11 14:57:15 UTC 2018
/dev/md0 /tmpRoot ext4 rw,relatime,journal_checksum,data=ordered 0 0
none /sys/kernel/debug debugfs rw,relatime 0 0
sys /sys sysfs rw,relatime 0 0
none /dev devtmpfs rw,relatime,size=16471572k,nr_inodes=4117893,mode=755 0 0
proc /proc proc rw,relatime 0 0
linuxrc.syno executed successfully.
Post init
DiskStastation login: