Crystal clear, thank you, Scott.
WBR, Sergey
Scott Rohling <[email protected]>
Sent by: Linux on 390 Port <[email protected]>
28-04-15 19:58
Please respond to Linux on 390 Port
To: [email protected],
cc:
Subject: Re: VM EDEVICE multipath for Linux
In the case of a minidisk allocated from an EDEVICE -- you only have a
single path to work with on the Linux guest...
z/VM will use multipathing for the EDEVICE to handle IO requests coming
from several guests/minidisks using the EDEVICE -- but each guest can only
queue one io on each minidisk allocated from the EDEVICE (there is only a
single address for the minidisk). If you want to have true multipathing
at the Linux level - you'll have to use directly attached FCP
subchannels...
Scott Rohling
On Tue, Apr 28, 2015 at 8:10 AM, Sergey Korzhevsky <[email protected]>
wrote:
> Hi Rob,
>
> Do i understand you right, that there is no performance boost in case
> of multipathing EDEV, only failover?
> In Linux, we have both, am i corect?
>
> Thank you.
>
> WBR, Sergey
>
>
>
>
> Rob van der Heij <[email protected]>
> Sent by: Linux on 390 Port <[email protected]>
> 28-04-15 17:49
> Please respond to Linux on 390 Port
>
> To: [email protected],
> cc:
> Subject: Re: VM EDEVICE multipath for Linux
>
>
> On 28 April 2015 at 16:38, Sergey Korzhevsky <[email protected]>
wrote:
>
> Any idea why " The Virtualization Cookbook for IBM z/VM 6.3, RHEL 6.4,
and
> > SLES 11 SP3" (latest, i think) does not mention this setup?
> > Maybe there some hidden problems?
> >
> >
> One of the challenges is performance, since there's only one I/O at a
time
> on an EDEV disk. If you're doing very large disks, that can get a
> bottleneck. Some installations use EDEV for the operating system and the
> application code (to simplify provisioning) and use native FCP for the
> application data (if any).
>
> Rob
>
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