[Xen-devel] [RFC] To promote PV SCSI posted before ...

[Tomonari Horikoshi <t.horikoshi@xxxxxxxxxxxxxx>]

Hi all.

To promote PV SCSI posted before, I post this patch.

http://lists.xensource.com/archives/html/xen-devel/2007-07/msg00450.html
http://lists.xensource.com/archives/html/xen-devel/2007-07/msg00451.html
http://lists.xensource.com/archives/html/xen-devel/2007-07/msg00452.html
http://lists.xensource.com/archives/html/xen-devel/2007-07/msg00453.html
http://lists.xensource.com/archives/html/xen-devel/2007-07/msg00561.html

PV SCSI has the structure like VBD.
Frontend driver is registered as SCSI HBA driver by Guest OS,
it passes SCSI CDB as is by using RING.
Frontend driver accesses all disks connected with 1HBA of Dom0.
Now, the whole of 1HBA of Dom0 is used by the guest
but in the future, 1HBA will be able to be shared with some Guest OS by NPIV. 
(see, http://www.xensource.com/files/xensummit_4/Xen_Summit_8_Matsumoto.pdf)


I activated some SCSI devices( tape drive, media changer) by using
this PV-on-HVM(PV SCSI). So Guest domain can backup data to tape
directly. And Guest domain works as a Backup Server by this function．

* LTO Tape Library ( Ultrium 2 drive of FC )
  # cat /proc/scsi/scsi
  Attached devices:
  Host: scsi0 Channel: 00 Id: 00 Lun: 00
    Vendor: HP       Model: Ultrium 2-SCSI   Rev: F45H
    Type:   Sequential-Access                ANSI SCSI revision: 03
  Host: scsi0 Channel: 00 Id: 00 Lun: 01
    Vendor: HP       Model: Ultrium 2-SCSI   Rev: F45H
    Type:   Sequential-Access                ANSI SCSI revision: 03

* DAT Library (SCSI)
  # cat /proc/scsi/scsi
  Attached devices:
  Host: scsi0 Channel: 02 Id: 00 Lun: 00
    Vendor: LSI      Model: MegaRAID SAS RMB Rev: 1.02
    Type:   Direct-Access                    ANSI SCSI revision: 05
  Host: scsi6 Channel: 00 Id: 00 Lun: 00
    Vendor: HP       Model: C7438A           Rev: ZU68
    Type:   Sequential-Access



The performance of PVSCSI is almost the same as VBD.
The following value is a performance ratio of pvscsi and vbd.
( pv-scsi/vbd )

 random read:write=1:1 3disk 1prosecs/1disk 
  blksize =   8k  1.00
  blksize = 128k  1.00

 random read:write=1:1 3disk 5prosecs/1disk 
  blksize =   8k  1.08
  blksize = 128k  1.15

 sequential blksize=128k 1prosecs/1disk 
  read  = 0.85
  write = 0.93


Best regards,
Horikoshi

Attachment: pv-on-hvm-add_scsifront.patch
Description: Binary data

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