VM Best Practices: Difference between revisions

VM Best Practices (view source)

Revision as of 03:57, 28 November 2017

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→‎Maximum volumes per VM

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 === Maximum volumes per VM ===
-'''Avoid attaching more than three volumes to a VM'''.  This has been observed to lead to kernel timeouts which can affect any disk operations on those volumes and may have a cascading effect, and can render the VM effectively inoperative.  While using a data volume is advisable (see above), use only one and you can carve it up into multiple filesystems inside your VM, and expand it as necessary.
+'''Avoid attaching more than three volumes to a VM'''.  This has been observed to lead to kernel timeouts which can affect any disk operations on those volumes and may have a cascading effect, and can render the VM effectively inoperative.  While using a data volume is advisable in some cases (see above), use only one and you can carve it up into multiple filesystems inside your VM, and expand it as necessary.
 This has been observed on Arbutus (west.cloud.computecanada.ca) by multiple users, although it may be somewhat dependent on volume size.  In one case, 3 x 100GB volumes attached to a p4-6gb VM caused kernel timeouts whenever disk operations of any magnitude were attempted.  It was very difficult to copy more than 500MB of data between two filesystems, for example.
-As of 27 November 2017 it is being tested on East Cloud (east.cloud.computecanada.ca).
+Test of a similar situation was performed on East Cloud and with 4 x 100GB data volumes (along with the root volume), the same OS and a similar VM flavour, the issue did not occur.  This VM had more memory (15 GB instead of 6 GB) but high memory usage was not observed in the Arbutus case and this isn't believed to be a factor.