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Poor performance disk array on Xen Serwer 7.2 and 7.5

Krzysztof Weber




I have a problem with slow copying on the same disk and the same VM on Xen Server 7.2 or 7.5. The transfer of copied data does not exceed 30 MB / s and often stops.

My hardware:

HPE 3PAR 8000 disk array with SSD drives.

Server located in C7000, Blade Gen 8 enclosure.


Please, suggest where the problem may be? The operating system has been eliminated.


Thank You.


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8 answers to this question

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Thank You for reply. I have 12 GB allocated to Dom0.

Data copying takes place within the same machine and the same disk, and a second disk mounted to the same machine within the same matrix. Measured with embedded tool in Windows 10 / Windows 2012 SRV. Also tested with the HD-Tune application.


What information is still needed to determine something?

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How about providing details on the RAID configuration (type and numbers of disk, RAID layout, size of each disk, how the array is attached -- iSCSI, NFS, etc.). Try also running top and/or xentop so you can monitor system activity when you see this slow I/O behavior. Is XenTools properly installed on the VMs? Have all required hotfixes been applied to the hosts?


Seriously, if you want help you need to provide way more details upfront. There are a lot of reasons why I/O can be slow and different system components can all contribute in various ways.

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The array is connected by FC, there are 16 SSD 600 GB disk drives in raid 6. On matrix side, there is 8x8 Gbit and 2x8 Gbit on blade side. In c7000 there are 4x8 Gbit interfaces.

Xen Center say that xentools is properly installed on VM. Any hotfixes is applied.


Thank you for suggestions.




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You can start by running "iostat -x 10" or iostat with some other appropriate flags to show your I/O stats on your pool master host. In particular, the queue size, iowait and read and write times are of interest. If you run top on the pool master, as well, you can check to see if it's not running out of memory or CPU cycles.



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We tested copying by looking at iostat and top. The files are attached. In general, the transfer drops suddenly after reaching a certain value, in the next copying with a large file the speed is very poor.
Does anyone have any suggestions on what else to check or what could be the reason?



















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