user1219721's questions

I need to set up a VPN.

I experimented with PPTP, but I got a lot of problems. VPN connection doesn't work behind some routers or mobile / wifi connections.

So I'm looking for a failsafe VPN solution. Something that should always work, no matter where we are. Just like SSH or HTTP.

Any ideas ?

They looks the same. It's SFF-8470

Is it ok to buy a "10Gbase-CX4" cable for an infiniband network ?

I got an application whose bottleneck is memory bandwidth.

Did some bench with i7 3820. It's much faster with 2400MHz than 1600MHz RAM.

Could Xeon E5-2670 handle faster ram than 1600MHz (non ECC) ?

I'm running WRF weather model. That's a ram intensive, highly parallel application.

I need to build a HPC cluster for that. I use 10GB infiniband interconnect.

WRF doesn't depends of core count, but on memory bandwidth. That's why a core i7 3820 or 3930K performs better than high-grade xeons E5-2600 or E7

Seems like universities uses xeon E5-2670 for WRF. It costs about $1500. Spec2006 fp_rates WRF bench shows $580 i7 3930K performs the same with 1600MHz RAM.

What's interesting is that i7 can handle up to 2400MHz ram, doing a great performance increase for WRF. Then it really outperforms the xeon. Power comsumption is a bit higher, but still less than 20€ a year. Even including additional part I'll need (PSU, infiniband, case), the i7 way is still 700 €/cpu cheaper than Xeon.

So, is it ok to use "gamer" hardware in a HPC cluster ? or should I do it pro with xeon ?

(This is not a critical application. I can handle downtime. I think I don't need ECC?)

Does Xeon Phi coprossesors works with i7 CPUs ?

It's advertised for use with Xeons, but for my app (WRF), i7-3930k performs better and is 3 times cheaper than high grade xeons. So I wonder if I could use Xeon Phi with an i7 cpu ?

I got Infiniband running on RHEL 6.3

[root@master ~]# ibv_devinfo 
hca_id: mthca0
transport:          InfiniBand (0)
fw_ver:             4.7.927
node_guid:          0017:08ff:ffd0:6f1c
sys_image_guid:         0017:08ff:ffd0:6f1f
vendor_id:          0x08f1
vendor_part_id:         25208
hw_ver:             0xA0
board_id:           VLT0060010001
phys_port_cnt:          2
    port:   1
        state:          PORT_ACTIVE (4)
        max_mtu:        2048 (4)
        active_mtu:     2048 (4)
        sm_lid:         2
        port_lid:       3
        port_lmc:       0x00
        link_layer:     InfiniBand

    port:   2
        state:          PORT_DOWN (1)
        max_mtu:        2048 (4)
        active_mtu:     512 (2)
        sm_lid:         0
        port_lid:       0
        port_lmc:       0x00
        link_layer:     InfiniBand

but it's only working as root.

when trying from a non-super user, I got nothing :

[nicolas@master ~]$ ibv_devices
device                 node GUID
------              ----------------
mthca0              001708ffffd06f1c

So, how to allow regular users to use infiniband ?

I need to upload file on a specific interface. This cannot be set-up via iptables, because my script output on several interfaces.

this is working fine :

scp -oBindAddress=192.168.100.1 ...

but

rsync --address=192.168.100.1

is still sending on eth0 (192.168.10.1)

how could I force rsync to use 192.168.100.1 ?

any idea ?

I need to transfer a number of files files over a low-quality broadband link to a server. The files are large, and take approximately 30 minutes to transfer per file.

I use scp, but it sometimes hangs -- the transfer doesn't fail with an error, it keeps running, but no further data is transferred.

So, I'm looking for a "failsafe" upload solution, one that will work even if the link fails for a few minutes or is otherwise unreliable.

My idea is:

1. split big file in small parts
2. upload parts, with timeout and retry if fail

Questions:

• is there a ready-to-run tool that implements this idea? (no specific need for scp. could be ftp or anything else)
• is there a way to detect when scp hangs? ((that is, it is still running, but does not transfer data)

I got three gateways:

192.168.10.1 on eth0  (default),
192.168.100.1 on eth0:0
192.168.101.1 on eth0:1

I'm trying to make my computer decide on which to use, from the request port. (request comes server-side)

exemple.com:80 -> via 192.168.10.1  to exemple.com:80
exemple.com:81 -> via 192.168.100.1 to exemple.com:80
exemple.com:82 -> via 192.168.101.1 to exemple.com:80

how should I proceed ?

thanks

I got data on a private FTP server I want to mirror it, but "on demand". My frontend is an Apache/PHP server...

Here's the flow :

• Clients asks the apache server for a file
• if file is not on hdd, download it from the ftp server. (stream it to client, while saving it to hdd)
• send file to client (from apache)

I don't know exactly how to proceed...

Is there a way to stream a file while downloading it ?

Maybe we could do something with php/curl...