IBM SR-BR10i RAID Controller too slow with VMware ESXi

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I'm transferring a virtual machine from one ESXi host to another using SSH on both ESXi Servers.

But it's painful slow, it's a massive 750GB .vmdk disk image, the VM is stopped (with downtime) and with 5.5MB/s speed ratio it will take more than one day com complete the move.

Am I missing something?

myvm.mydomain.com-flat.vmdk                 26%  200GB   5.4MB/s 29:09:06 ETd

Important hardware on the ESXi Server:

Supermicro X9SCM-F
Intel 82574L Gigabit Controller
IBM SR-BR10i RAID Controller
2x WD Velociraptor WD1000DHTZ (RAID1 mode from controller)

Another point: I've built the and synchronised the RAID array before start VM migration.

Thanks for any help,

Best Answer

If you think the copy is slow, you have not seen the VM run yet. The major trouble is that your controller is missing a BBU and ESXi is doing many synchronous writes (where the controller's or disk's write cache which otherwise might have been of use is circumvented to ensure data consistency).

Add a BBU (if available as an option) or replace the controller with a model using BBWC/FBWC. Or, if you do not care about the integrity of the data (mind that this might result in losing the entire data store if your host loses power in an untimely moment), you could enable the write-back cache even for synchronous writes using lsiutil. Some guy has even done a compile for ESXi, so you likely would not even need to reboot to another OS to try it out.

Other than that, ESXi-internal scp/cp operations are rather slow, you should pick a different approach:

  • For performance and data placement reasons, do not use scp or cp; instead, use vmkfstools, the Virtual Machine Importer tool from VMware, or the SDK APIs to manipulate your virtual disks. You should see very significant performance improvements if you use the recommended tools.

If you can't go with one of the mentioned tools, consider Veeam's FastSCP which is also meant to improve SCP copy performance.

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