Known Issues

The following is intended to make DataCore Software users aware of any issues that affect performance, access or may give unexpected results under particular conditions when SANsymphony is used in configurations with Microsoft Windows Hosts.

These Known Issues may have been found during DataCore’s own testing but others may have been reported by our users when a solution was found that was not to do with DataCore’s own products.

DataCore cannot be held responsible for incorrect information regarding another vendor’s products and no assumptions should be made that DataCore has any communication with these other vendors regarding the issues listed here.

We always recommend that the vendor’s should be contacted directly for more information on anything listed in this section.

For ‘Known issues’ that apply to DataCore Software’s own products, please refer to the relevant DataCore Software Component’s release notes or user guides.

Unless explicitly stated:

Windows 2008 includes both the SP2 and 'non-SP2' versions

Windows 2012 includes both the R2 and 'non-R2' versions

MPIO – Microsoft and DataCore WIK

Affects Windows 2008 / 2012 / 2012 R2 / 2016 with updates older than July 2017

Microsoft's multipath bus driver (MPIO.sys) may not failover if two or more paths from a Host to a Virtual Disk fail at the same time, or if the same Virtual Disk for two or more paths is unavailable.

This will affect Hosts using either DataCore's MPIO (e.g. the DataCore Windows Integration Kit) or Microsoft's own 'built-in' MPIO - both of which rely on the MPIO.sys driver of the Windows operating system.

The Microsoft MPIO.sys driver builds its own list of all paths to any given disk device (e.g. a Virtual Disk) which also includes the path that is designated as the 'next' path available for failover if the active path (e.g. the path that is being used at that moment to send IO) reports an error either on the path or to the disk device itself. If an event, such as a disk device or connection failure, cause both the active and the 'next' path (determined by the MPIO.sys driver) to lose access to the same disk device, then no failover will occur even if there are other paths available to that same disk device.

In this case the Host will lose access to the Virtual Disk.

This issue was fixed in the following Windows updates:

For Windows 2019:

N/A – Windows 2019 was not released when this issue was discovered and then fixed. Therefore, all Windows 2019 installations are unaffected by this problem.

For Windows 2016:

Fixed in any Windows Update after June 27, 2017—KB4022723

"Addressed issue where you may lose access to storage disks when there are still available paths if there is an error on one of the multipath I/O paths."

For Windows 2012 R2:

Fixed in any Windows Update after July 11, 2017—KB4025336 (Monthly Rollup)

"Addressed an issue where MPIO failover stops after a disk has been surprise removed, identified by Event ID 157: "Disk X has been surprised removed" when there are still viable paths to use. Scenario may occur when the newly selected path belongs to the disk that has been surprised removed."

For Windows 2008 / 2012 (non-R2):

No fix from Microsoft was ever issued for either of these versions of Windows Server. Therefore, as the problem is in Microsoft's own multipath bus driver, and because it is impossible for DataCore to know which is going to be the 'next' designated active path at any given moment (as this is decided by the MPIO.sys driver) the only safe configuration which will guarantee failover is when a mirrored Virtual Disk is served to only one Host (FE) port from each DataCore Server.

Affects Windows 2008 / 2012 / 2012 R2

Hosts using DataCore Windows Integration Kit or DataCore's MPIO do not use the Preferred DataCore Server immediately after a restart.

The host's operating system scans for the first available hardware path as it starts up and uses it regardless if the path is on the preferred DataCore Server or not. The device path discovery is usually decided by the order of the Host's PCI slots in the Host Server and is beyond the control of the DataCore MPIO software. Once all available device paths have been detected by the host however, the Host will (eventually) move over to the path on the 'preferred' DataCore Server.

Microsoft Cluster Services (MSCS)

Affects Windows 2008 / 2012 / 2012 R2

The Microsoft Cluster Validation test may report a warning message about an unsigned DataCore Multipath driver (even though the driver is signed).

Microsoft has confirmed that in this case this message is benign and can be safely ignored and they will support MSCS with the latest version of DataCore Windows Integration Kit.

Fibre Channel

Affects Windows 2008 / 2012 / 2012 R2 / 2016 / 2019

16 GB QLogic Fibre Channel Host Bus Adaptors

Do not use driver version 9.1.17.21 with firmware older than 08.03.00 when connecting to DataCore Server Front-end ports using SANsymphony-V versions 10.0 PSP 4 Update 1 or earlier as in some cases this firmware on the Host can cause the DataCore Server to crash.

Affects Windows 2008 / 2012 / 2012 R2 / 2016

2 or 4 GB QLogic Fibre Channel Host Bus Adaptors

Do not use driver versions 9.0.1.12 or 9.0.2.11 as they may cause unexpected disconnections from the DataCore Server.

ODX and SCSI UNMAP/TRIM

Affects Windows 2008 / 2012 / 2012 R2 / 2016 / 2019 / 2022

Off Load Data Transfers (ODX) will not be used for files smaller than 256 Kb

File transfers for files smaller than 256 kb will take place using 'traditional' copy methods so large numbers of these small, files may impact Host performance for the duration of the transfer. See:

Offloaded Data Transfer

Affects Windows 2012 / 2012 R2 / 2016 / 2019 / 2022

Formatting a Virtual Disk may take longer than expected.

During the formatting of any filesystem, Windows will (by default) issue SCSI UNMAP write I/O for the entire size of the filesystem. This will mean that the filesystem format process may take a long time to complete and will generate significant write I/O to the Disk Pool regardless if the 'Perform a quick format' option is checked or not. The recommendation from DataCore is to disable the 'SCSI TRIM and UNMAP' feature on the Windows Host just for the duration of the format.

Method 1:

  1. From a CMD window on the Host, run the fsutil command:

    This disables all the UNMAP commands from the Host.
  2. After the format has completed, re-enable the UNMAP feature by running the command:

    The command takes effect immediately and without any impact on the Windows Host.
  3. To verify the current setting for UNMAP, run the command:

    DisableDeleteNotify=0 - indicates the UNMAP feature is enabled
    DisableDeleteNotify=1 - indicates the UNMAP feature is disabled

    Disabling UNMAP will not affect the Windows ODX (offline data transfer) feature or vice versa.

Method 2:

  1. Create a virtual disk of size 1 GB and serve it to the host.
  2. Format the disk with NTFS on the host. The disk formatting should get completed quickly.
  3. Resize the virtual disk in SANsymphony to the desired size. Please ensure that the new size is larger than the original size.
  4. Rescan the host to view the size of the disk expand.
  5. Extend the NTFS volume to the desired size. The NTFS partition should get extended quickly.