iSCSI Mirroring Performance

[Bill.French]

I'm evaluating StarWind and currently setting up an iSCSI mirror to a remote iSCSI target.

One thing that was a little frustrating, once I set up the mirror, a progress bar popped up and fairly quickly moved to 100% .... then sat there, for hours - at least six hours. I left it over night, and it cleared up and the setup was able to continue. I assume it was syncing up the data, which I can understand, but if the progress bar could reflect that progress, that would be great, so that I can try and plan my day around roughly how long it is going to take.

Also, along those lines, is it possible to get some insight into how the mirror is performing? I'm syncing a 300GB image over a fairly slow connection (45Mb) so I'd like to observe how the syncing is doing. Changes within an hour might be 6GB, but probably less.

Thanks!! --Bill

[Bohdan (staff)]

Hello Bill,
Are your first and the second mirror images local files or one of theme is placed on the remote host?
Did you check Create new checkboxes to create new image files or you use existing images?
What option did you check Clear mirrors or Synhronize mirrors data?
If one of your mirrors is remote what caching options did you set?
We need to know your exact configuration steps to give you the right answer.

[Bill.French]

1. It is a remote mirror
2. I created new image files
3. I chose "clear mirrors"
4. I enabled caching, and set them up as "slow link"

Thanks! --Bill

[Bohdan (staff)]

Bill,

If the remote mirror is shared using StarWind server then the local server sends command "clear image file" to the remote one. In this case the performance depends on only your hdd. Let your hdd speed is 20 MBs/s. So it takes (300 Gb)/(20 MBs/s)=300*1024/20=15360s=256m ~ 4.3 hours to fill the image file with zeroes.
But if the remote server is not the StarWind server then local server fills the remote image with zeroes through the network interface. In this case the performance depends on your network speed and hdd speed.

As for progress bar, we'll check it in our test lab and fix it if the problem be reproduced.

Slow channel mode improves performance of slow networks because it performs caching of read and write operations and the full synchronization takes place when mirror is disconnected.