Hardware server requirements?

[maximaler]

Hello, I have problem with perfomance on the server.
When the player reaches the defect 30+, the server begins to lag
What could be the problem?

Hosting specs:
- KVM (Kernel-based Virtual Machine)
- Ubuntu-14.04-x86_64-minimal
- x6 Intel Xeon E5620, 2.4Ghz
- 3GB RAM
- 30GB SSD

Server:
- 10 addons
- Instal with help [URL="https://gameservermanagers.com/lgsm/gmodserver"]LGSM[/URL]

Config:

// Network Settings
sv_downloadurl ""
sv_loadingurl "http://novus.myarena.ru/scp/loading.php?steamid=%s&mapname=%m"
net_maxfilesize 64
sv_maxrate 40000
sv_minrate 40000
sv_maxupdaterate 66
sv_minupdaterate 10
sv_maxcmdrate 60
sv_mincmdrate 10

// Server Settings
sv_airaccelerate 100
sv_gravity 600
sv_allow_wait_command 0
sv_allow_voice_from_file 0
sv_turbophysics 0
sv_max_usercmd_future_ticks 12
gmod_physiterations 4
sv_client_min_interp_ratio 1
sv_client_max_interp_ratio 2
think_limit 20
sv_region 0
sv_noclipspeed 5
sv_noclipaccelerate 5
sv_lan 0
sv_alltalk 1
sv_contact [e-mail]
sv_cheats 0
sv_allowcslua 0
sv_pausable 0
sv_filterban 1
sv_forcepreload 1
sv_footsteps 1
sv_voiceenable 1
sv_voicecodec vaudio_speex
sv_timeout 120
sv_deltaprint 0
sv_allowupload 0
sv_allowdownload 0

Thank you!