VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
Magnetic disk considerations
While there is no need to check drivers/firmware of your hard disk drives (HDD aka
magnetic disks), one should continue to check that the SAS or SATA drives planned
for the Virtual SAN deployment are supported. The main feature of the drives is the
RPM, revolutions per minute. RPMs are as follows:
Drive Type
RPM
NL-SAS (Near line SAS) 7200
SAS 10000
SAS 15000
SATA 7200
As you can see, SAS drives can perform much better than NL-SAS and SATA, with the
only NL-SAS and SATA disks being 7200 RPMs. NL-SAS disks, which are basically
SATA disks with a SAS daughter card, should be treated just like SATA disks. They
have the same performance and characteristics as SATA drives. For performance at
the magnetic disk layer, serious consideration should be given to the faster SAS
drives.
External storage enclosure considerations
Blade servers are becoming increasingly popular but these do not use direct
attached storage for the most part. Most blade server deployments use external
storage enclosures.
VMware is supporting limited external storage enclosure configurations in the 6.0
versions of Virtual SAN. Once again, if you plan to use external storage enclosures
with Virtual SAN, ensure the VCG is adhered to with regards to versioning for these
devices. Customers will be expected to configure the externals storage enclosures
such that a disk is only visible to one host.
Processor power management considerations
While not specific to Virtual SAN, processor power management settings can have
an impact on overall performance. Certain applications that are very sensitive to
processing speed latencies may show less than expected performance when
processor power management features are enabled. A best practice is to select a
‘balanced’ mode and avoid extreme power-saving modes. There are further details
found in VMware KB article 1018206.
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