iSCSi Transfer Speed Drop

Hello all,

I've been using FreeNAS for my home nas for quiet some time now. I have recently entered into new territories, such as iSCSi. What I've noticed through my first few file transfer tests, is that the transfer speed starts at a strong 75-80 MB/s, then after 3-5 seconds after the start of the transfer, the rate rapidly declines to around 10 MB/s. What can I do to prevent this drop in speed? Or, is this to be expected? Currently, I have a 64x version of FreeNAS running through Virtual Box. If there is any relivent information that i should post, please tell me. 

Thanks in advanced,


what's the client os? I have had this kind of thing before on windows 7 and 8, it can have to do with having a media player open (or IE), or with "green ethernet" being enabled on the client, and that sort of thing. You can use wireshark to do a packet capture and see if you're getting errors, and you can also do an hdparm -t /path/to/volume while you're copying at the slower speed to see if it drops lower (probably shouldn't)

sometimes this can be problems with interrupt flooding and things like that if you dont have a good nic in the freenas box. Intel nics in the freenas box? what's in the iscsi machine? 

Thank you for the quick reply Wendell,

The client os is a windows 8 mechine. According to task manager, I do not see any instances of IE or windows media player. To the best of my knowledge, I do not think any type of "green ethernet" is running. I have had some experince with Wireshare from a pervious Debian mechine, and will try to see if I can find anything through it. I will also try to do an hdparm command during differnet stages of the transfer. The nic inside the iSCSi mechine is just an on-board nic from a Gigabyte 990fxa-ud5 (Realtek 8111E) Some other quick info on the server side include: an AMD 8350 processor, and a Samsung 840 SSD.

Update: Wireshark does not report anything unusual through 3 different read transfers. As for hdparm, as you may already know, is not  a native command for windows. Should I Download a 3rd party software for it? As for freenas, the server reports it as an unknown command. Is there a way to use hdparm on freenas that I'm unaware of? I do not have a Linux based system at my disposal at the moment, but if it is necessary, I could easily setup a quick system on Virtual Box.

Right, freebsd, sorry. Diskinfo.. diskinfo is what you want probably. google that, run it.

But. I think we found your problem. Realtek 8111e eh?

Put an intel PCIe nic in your freenas box at once. That'll fix you up quick.


Haha nice touch with Will Ferrell. 

Will do. On hand, I have an Intel PCI nic that I'll throw in this afternoon and do some testing. This afternoon, I will also run diskinfo -t /path/to/extent. Expect my update in roughly 9- 10 hours.

To start off, I would like to state that the Intel card I'm using is dated, and possibly could be damaged. I have repeated the transfer test 3 separate times, with all of them concluding in similar readouts. The replacement Intel card I used is an Intel Pro 1000 MT card (PCI). The transfer speed replicated the original, showing roughly 80 Mb/s start, and a drop to 10 Mb/s ending speed. The diskinfo -t command reports 360 Mb/s before transfer, 205 Mb/s during the high speed part of transfer, 180 Mb/s during the slow part of transfer, and 195 Mb/s immediately after the transfer.(exact output below) To be honest, I do not understand completely what all this data means, but I'm confident you could interpret it better then I can. If necessary, I can buy a new Intel nic from a local Best Buy or Micro Center. According to what I understand, the Intel nic has made no impact. As I've stated previously, I am unaware of any green ethernet utility running, but it is still possible one may be running. 

Before Transfer

Before Transfer

High Speed During Transfer

Low Speed During Transfer

After Transfer

Does the network driver have any options that you can set? 


I just had an issue with my home server with transfer speeds were not full gigabit and running around 600Mbps.... Needless to say the Intel pro 1000/pt drivers had the Offload functions enabled. I disabled the following:

TCP checksum offload

IPv4 Checksum Offload

after that the ports run constant at 980Mbps..... Close Enough for me...

If you can configure the drivers maybe look into doing this... just a thought