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<div class="moz-cite-prefix">On 08/30/2017 12:35 PM, Ulrich Windl
wrote:<br>
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<pre wrap="">Ferenc Wágner <a class="moz-txt-link-rfc2396E" href="mailto:wferi@niif.hu"><wferi@niif.hu></a> schrieb am 30.08.2017 um 10:51 in Nachricht
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<pre wrap=""><a class="moz-txt-link-rfc2396E" href="mailto:87h8wpa16c.fsf_-_@lant.ki.iif.hu"><87h8wpa16c.fsf_-_@lant.ki.iif.hu></a>:
[...]
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<pre wrap="">Do you mean the LVM metadata read latency as seen by the LVM tools or
that of a mirrored data region?
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<pre wrap="">[...]
Actually I monitor all of these:
(on the VM host)
* the Multpath devices for the SAN storage that provide the PVs
* the mirrored LV that provides VM storage
* the mirror logs of the LV
* the OCFS2 filesystem that hosts the VM files and devices
(on the VM guest)
* the virtual physical disk"
* the fileystem on top of it
An amazing side note: For comparison I monitor NFS latency in a VM-based
NFS-client where the server is physical, and the delays are a lot more constant
than for the virtual local disks (see attachment).</pre>
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Which would mean that at least part of the latency is due to<br>
basically unnecessary synchronization effects.<br>
Given that the history of making everything asynchronous and<br>
decoupled is much longer for networking than for block/filesystem-<br>
layers ...<br>
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Regards,<br>
Klaus<br>
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Regards,
Ulrich
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