Mailing List Archive: Xen: API

SG_IO for iscsi targets in XCP

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george.shuklin at gmail

Jul 19, 2011, 3:58 AM

Post #1 of 3 (335 views)
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SG_IO for iscsi targets in XCP

Good day.

I'm researching if XCP by anyway is issuing some SCSI commands like
reservation or persistent reservation. I done 'greping' via source code
for SG_IO ioctl() and found just few innocent inquiry/id requests.

Just to be sure: Is any SCSI-specific features used in XCP for cluster
management or resource locking? Or iscsi used only as generic block
device with LVM?

Thanks.

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Dave.Scott at eu

Jul 19, 2011, 4:21 AM

Post #2 of 3 (319 views)
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RE: SG_IO for iscsi targets in XCP [In reply to]

Hi George,

XCP just uses shared LVM over iSCSI as a generic block device. This is only safe because (i) we modified LVM to run in a "read-only" mode on slaves; and (ii) we co-ordinate all LVM metadata updates across the pool in the XCP storage layer.

Cheers,
Dave

> -----Original Message-----
> From: xen-api-bounces [at] lists [mailto:xen-api-
> bounces [at] lists] On Behalf Of George Shuklin
> Sent: 19 July 2011 11:58
> To: xen-api [at] lists
> Subject: [Xen-API] SG_IO for iscsi targets in XCP
>
> Good day.
>
> I'm researching if XCP by anyway is issuing some SCSI commands like
> reservation or persistent reservation. I done 'greping' via source code
> for SG_IO ioctl() and found just few innocent inquiry/id requests.
>
> Just to be sure: Is any SCSI-specific features used in XCP for cluster
> management or resource locking? Or iscsi used only as generic block
> device with LVM?
>
> Thanks.
>
>
> _______________________________________________
> xen-api mailing list
> xen-api [at] lists
> http://lists.xensource.com/mailman/listinfo/xen-api

george.shuklin at gmail

Jul 19, 2011, 5:33 AM

Post #3 of 3 (345 views)
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RE: SG_IO for iscsi targets in XCP [In reply to]

Thank you very much.

I feel more safe now with dual primary DRBD configuration. I'll report
results of practical deployment with real-life load later.

В Втр, 19/07/2011 в 12:21 +0100, Dave Scott пишет:
> Hi George,
>
> XCP just uses shared LVM over iSCSI as a generic block device. This is only safe because (i) we modified LVM to run in a "read-only" mode on slaves; and (ii) we co-ordinate all LVM metadata updates across the pool in the XCP storage layer.
>
> >
> > I'm researching if XCP by anyway is issuing some SCSI commands like
> > reservation or persistent reservation. I done 'greping' via source code
> > for SG_IO ioctl() and found just few innocent inquiry/id requests.
> >
> > Just to be sure: Is any SCSI-specific features used in XCP for cluster
> > management or resource locking? Or iscsi used only as generic block
> > device with LVM?

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