XenServer Export Performance Seems Poor

Dashrender

@Dashrender

Doesn't answer your export question, but something I came across:
https://xen-orchestra.com/blog/xenserver-backup-compress-or-not-compress/

Cool thanks - and you're right, While he does say export in the opening line, he's not talking about a single export, he's talking about backups.

I love the more or less one button push to create a one time export/backup of the system, it would be nice though to get a prompt for options (compressed/not compressed). I also wonder - is it efficient to download the "export" through the browser download instead of a direct push like the backup function uses? i.e. is the browser adding any overhead?

With that in mind an option of what pre-mapped mountpoint (network or local) to save to, and compress or non-compress would be to great options to see for the "export" option.

Dashrender

A little more than 5 hours and 270 GB done.

It seems to be going about 2 times faster, maybe 3.

BRRABill

@Dashrender said:

I love the more or less one button push to create a one time export/backup of the system, it would be nice though to get a prompt for options (compressed/not compressed). I also wonder - is it efficient to download the "export" through the browser download instead of a direct push like the backup function uses? i.e. is the browser adding any overhead?

Right, since this basically is a full backup that is being downloaded to your browser.

olivier

@Dashrender In any case, it's not a "full" direct push: it goes through xo-server, since we can't tell XenServer to push itself a VM somewhere. In fact, export is always working in "pull": a HTTP handler is opened by XAPI, and listen for HTTP GET request.

This is valid for everything, xe, XenCenter, XO export through your browser, XO backups etc.

So it's not really an overhead with your browser, xo-server just act as a proxy to deliver your file (so if you don't have network bottleneck between you and xo-server that's OK:

XenServer --> xo-server --> browser

A backup will do:

XenServer --> xo-server --> remote point

But as I said, in any case, xo-server will do a HTTP GET.

The main bottleneck is Gzip compression first. If you disable it, that's another potential bottleneck: the XAPI HTTP handler speed.

Note: the possibility to ask XAPI to push a backup somewhere will be discussed with the XAPI team during Xen Hackathon. IDK if they could do something, but I'll be at their office to explain the issue, in front of the whole dev team.

olivier

By the way you can rename the topic title

Dashrender

@olivier said:

By the way you can rename the topic title

What would you propose?

The title is calling out XenServer, not XO, and as you've stated this is an actual known issue within XS. I'm definitely open to suggestions for a title change though.

Dashrender

@olivier said:

@Dashrender In any case, it's not a "full" direct push: it goes through xo-server, since we can't tell XenServer to push itself a VM somewhere. In fact, export is always working in "pull": a HTTP handler is opened by XAPI, and listen for HTTP GET request.

This is valid for everything, xe, XenCenter, XO export through your browser, XO backups etc.

So it's not really an overhead with your browser, xo-server just act as a proxy to deliver your file (so if you don't have network bottleneck between you and xo-server that's OK:

XenServer --> xo-server --> browser

A backup will do:

XenServer --> xo-server --> remote point

But as I said, in any case, xo-server will do a HTTP GET.

The main bottleneck is Gzip compression first. If you disable it, that's another potential bottleneck: the XAPI HTTP handler speed.

Note: the possibility to ask XAPI to push a backup somewhere will be discussed with the XAPI team during Xen Hackathon. IDK if they could do something, but I'll be at their office to explain the issue, in front of the whole dev team.

Thanks for the explanation. I look forward to what you can share after your discussion about the HTTP handler.

Dashrender

The 700 GB VM was backed up in 13 hours 50 mins with the following setup:
compression disabled
1 GB same switch transfer
SMB sharing protocol
4 TB WD Red drive (single drive) as the target
Windows 7 x64 4 GB RAM

This was 50% faster than using the export feature which enables GZIP and I was saving to a USB 3.0 device.

Dashrender

OK starting last test.

backup compress disabled
Win7 x64 4 GB RAM
1 GB same switch transfer
SMB sharing
2 TB USB 3.0 drive

Started at 9 AM CDT

JaredBusch

@Dashrender said:

OK starting last test.

backup compress disabled
Win7 x64 4 GB RAM
1 GB same switch transfer
SMB sharing
2 TB USB 3.0 drive

Started at 9 AM CDT

I would expect this one to be the same as the last. I doubt you are hitting any kind of bottleneck on the target media.

Dashrender

@JaredBusch said:

I would expect this one to be the same as the last. I doubt you are hitting any kind of bottleneck on the target media.

Yeah, I'm already seeing that be the case. 2 hours in, 108 GB transferred.

olivier

@Dashrender The current title is perfect (didn't see the change before)

Dashrender

@olivier said:

@Dashrender The current title is perfect (didn't see the change before)

Maybe Scott edited it before, I haven't changed it since I posted it.

scottalanmiller

@Dashrender said:

@olivier said:

@Dashrender The current title is perfect (didn't see the change before)

Maybe Scott edited it before, I haven't changed it since I posted it.

Yeah, that was me

BRRABill

@Dashrender said

Yeah, I'm already seeing that be the case. 2 hours in, 108 GB transferred.

So around 15MBps is the max we can hope for?

Is that what you ended up determining?

Dashrender

I never tested again after this situation. Perhaps when I get back in the office I will try one.

BRRABill

I'm trying to figure out the quickest way to get a VM from one XS to another.

I'll ping @olivier again here, as I am sure XO is part of that discussion.

At least if you export it to your desktop you can follow the progress. But it seems like it does compression on the export, right? Is that was was ascertained from this thread?

Dashrender

@BRRABill said in XenServer Export Performance Seems Poor:

I'm trying to figure out the quickest way to get a VM from one XS to another.

I'll ping @olivier again here, as I am sure XO is part of that discussion.

At least if you export it to your desktop you can follow the progress. But it seems like it does compression on the export, right? Is that was was ascertained from this thread?

The is a way to do an export without compression. This site is not the easiest to look through on my kindle fire. I thought Oliver posted about it in this thread?

BRRABill

@Dashrender said

The is a way to do an export without compression. This site is not the easiest to look through on my kindle fire. I thought Oliver posted about it in this thread?

No, I looked through the whole thread and did not see it.

He only mentions turning it off for backups.

BRRABill

After some research today, I have come to the conclusion (could be wrong) that EXPORT does not compress. I came to this conclusion because a lot of the articles I saw spoke of compressing the export.

But it seems like it was said in the thread it IS enabled.

So confusing...

Take a look at this:
https://www.citrix.com/blogs/2009/02/10/xenserver-tips-and-tricks-minimize-the-size-of-your-exported-virtual-machines/

"In the interest of not overloading the system that is exporting the virtual machine we don’t compress the data that is exported. So to really save on space after you do an export you can then use your favorite compression program to shrink down the exported file even more. "