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 certain conditions when SANsymphony is used in configurations with Linux 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 vendors 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.
Formatting Virtual Disks
Affects all Linux Distributions
Formatting a virtual disk may take longer than expected
If the virtual disk is mounted on the Linux host using the -o discard mount option formatting the disk will automatically use ‘TRIM/UNMAP’ commands during the format process which can result in a significantly longer wait time for the format to complete.
Use either the mkfs command with the ‘nodiscard’ switch or mount the virtual disk without the –o discard option. Refer to the mkfs and mount man pages for your specific Linux distribution for more information.
Affects all Linux Distributions
Ext3 FS will use excessive disk pool Storage Allocations
The Ext3 filesystem will use significant amounts of Storage Allocation Units (SAU) during the ‘Writing superblocks and filesystem accounting information’ phase of the file system's creation. Care must therefore be taken so as not to completely use all the SAUs from the disk pool; and if Ext3 is required, then use a small (i.e., 4MB) SAU size. Other filesystem types do not seem to exhibit this behavior and use only a few SAUs during filesystem creation.
Redetecting Paths to Virtual Disks
Affects all Linux Distributions
A manual rescan on the host is needed to discover new paths after using SANsymphony’s evacuation feature.
See the section Evacuating a DataCore Server from the online help.
Symptoms include the host reporting "alua not supported" and/or "failed to read S.M.A.R.T. values" for evacuated virtual disks until the new paths are discovered.
Affects Ubuntu Only
Manual rescans are needed to update previously failed paths for Ubuntu hosts
During testing, DataCore have not been able to get Ubuntu to automatically re-detect paths to mirrored virtual disks that have failed or have been removed (e.g., after stopping a DataCore Server) and are then subsequently made available again. Manual intervention is required.
Use the 'multipath' command to establish which paths were previously failed (and are now available from the DataCore Server):
multipath -ll
Then use the 'echo' command to send an IOCTL to the disk device and ‘force’ the operating system to update the path’s status properly. For example:
echo 1 > /sys/block/sdc/device/rescan
Alternatively, download and install the 'scsitools' package and use the 'rescan-scsi-bus' command to re-establish the connection to the previously failed path.