12:09 p.m.
You can go with 512 emulation and later you can recreate the brick without that emulation
(if there are benefits of doing so).
After all, you gluster is either replica 2 arbiter 1 or a replica 3 volume.
Best Regards,
Strahil Nikolov
On Oct 1, 2019 09:26, Satheesaran Sundaramoorthi <sasundar(a)redhat.com> wrote:
On Tue, Oct 1, 2019 at 11:27 AM Guillaume Pavese
<guillaume.pavese(a)interactiv-group.com> wrote:
>
> Hi all,
>
> Sorry for asking again :/
>
> Is there any consensus on not using --emulate512 anymore while creating VDO volumes
on Gluster?
> Since this parameter can not be changed once the volume is created and we are nearing
production setup. I would really like to have an official advice on this.
>
> Best,
>
> Guillaume Pavese
> Ingénieur Système et Réseau
> Interactiv-Group
>
Hello Guillaume Pavese,
If you are not using --emulate512 for VDO volume, then VDO volume will be created
as 4K Native volume (with 4K block size).
There are couple of things that bothers here:
1. 4K Native device support requires fixes at QEMU that will be part of
CentOS 7.7.2 ( not yet available )
2. 4K Native support with VDO volumes on Gluster is not yet validated
thoroughly.
Based on the above items, it would be better you have emulate512=on or delay
your production setup ( if possible, till above both items are addressed )
to make use of 4K VDO volume.
@Sahina Bose Do you have any other suggestions ?
-- Satheesaran S (sas)
>
>
> On Fri, Sep 27, 2019 at 3:19 PM Sandro Bonazzola <sbonazzo(a)redhat.com> wrote:
>>
>>
>>
6:55 p.m.
New subject: [ANN] oVirt 4.3.6 is now generally available
Good idea Strahil.
I guess there could be benefits, as when I mailed vdo-devel in March asking
about emulate512 performance impact, the answer from RedHat's Michael
Sclafani was as follows :
Begin citation:
512 emulation was intended to support drivers that only do a fraction of
their I/O in blocks smaller 4KB. It is not optimized for performance in any
way. Under the covers, VDO is still operating on 4KB physical blocks, so
each 512-byte read is potentially amplified to a 4KB read, and each
512-byte write to a 4KB read followed by a 4KB write. A workload consisting
exclusively of 512-byte randomly-distributed writes could effectively be
amplified by a factor of 16.
We have a suite of automated tests we run in 512e mode on a nightly basis.
That suite is a subset of our regular tests, containing only ones we expect
would be likely to expose problems specific to the emulation.
There should be no penalty to having emulation enabled on a volume that no
longer uses it. If the I/O is 4KB-aligned and 4KB or larger, having it
enabled won't affect it.
It does not appear the setting can be modified by the VDO manager, but I
cannot remember at this moment why that should be so.
Best
Guillaume Pavese
Ingénieur Système et Réseau
Interactiv-Group
On Tue, Oct 1, 2019 at 6:07 PM Strahil <hunter86_bg(a)yahoo.com> wrote:
You can go with 512 emulation and later you can recreate the brick
without
that emulation (if there are benefits of doing so).
After all, you gluster is either replica 2 arbiter 1 or a replica 3 volume.
Best Regards,
Strahil Nikolov
On Oct 1, 2019 09:26, Satheesaran Sundaramoorthi <sasundar(a)redhat.com>
wrote:
On Tue, Oct 1, 2019 at 11:27 AM Guillaume Pavese <
guillaume.pavese(a)interactiv-group.com> wrote:
Hi all,
Sorry for asking again :/
Is there any consensus on not using --emulate512 anymore while creating
VDO volumes on Gluster?
Since this parameter can not be changed once the volume is created and we
are nearing production setup. I would really like to have an official
advice on this.
Best,
Guillaume Pavese
Ingénieur Système et Réseau
Interactiv-Group
Hello Guillaume Pavese,
If you are not using --emulate512 for VDO volume, then VDO volume will be
created
as 4K Native volume (with 4K block size).
There are couple of things that bothers here:
1. 4K Native device support requires fixes at QEMU that will be part of
CentOS 7.7.2 ( not yet available )
2. 4K Native support with VDO volumes on Gluster is not yet validated
thoroughly.
Based on the above items, it would be better you have emulate512=on or
delay
your production setup ( if possible, till above both items are addressed )
to make use of 4K VDO volume.
@Sahina Bose <sabose(a)redhat.com> Do you have any other suggestions ?
-- Satheesaran S (sas)
On Fri, Sep 27, 2019 at 3:19 PM Sandro Bonazzola <sbonazzo(a)redhat.com>
wrote:
--
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