td3201
Contributor
Contributor

vmfs vs mapped raw lun performance

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The following are two tests I ran inside a VM. One is to the OS drive which is inside a regular VMFS datastore, the other is to a mapped raw lun. Both are on the same backend storage (Equallogic iSCSI) connected via fixed MPIO 1 Gb/s. Should I be seeing that kind of difference and is 37 MB/s OK?

# dd if=/dev/zero bs=9000 count=100000 of=test && rm -f test

100000+0 records in

100000+0 records out

900000000 bytes (900 MB) copied, 8.83205 seconds, 102 MB/s

# dd if=/dev/zero bs=9000 count=100000 of=test && rm -f test

100000+0 records in

100000+0 records out

900000000 bytes (900 MB) copied, 23.9424 seconds, 37.6 MB/s

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td3201
Contributor
Contributor

Another question about thin provisioning. Would it only affect performance when the write is forcing the underlying vmdk to expand?

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mcowger
Immortal
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Yes. Any rewrite to an already allocated/zeroed block is no (extra) cost.

--Matt

VCP, VCDX #52, Unix Geek, Storage Nerd

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--Matt VCDX #52 blog.cowger.us
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