Yes please, assisting clusters in moving over to a 4k block size would be
On Tue, Feb 16, 2021 at 1:14 PM Josh Durgin <jdurgin(a)redhat.com> wrote:
Changing min_alloc_size in bluestore requires
redeploying the OSD.
There's no other way to regain the space that's already allocated.
In terms of making this easier, we're looking to automate rolling format
changes across a cluster with cephadm in the future.
On 2/16/21 9:58 AM, Steven Pine wrote:
Will there be a well documented strategy / method
for changing block
on existing clusters? Is there anything that
could be done to optimize or
assist clusters in the cut over?
On Tue, Feb 16, 2021 at 3:41 AM Loïc Dachary <loic(a)dachary.org> wrote:
> Hi Josh :-)
> Thanks for the update: this is great news and I look forward to using
> once Pacific is released.
> On 16/02/2021 00:43, Josh Durgin wrote:
>> Hello Loic!
>> We have developed a strategy in pacific - reducing the min_alloc_size
> for HDD to 4KB by default.
>> Igor Fedotov did a lot of investigation and benchmarking, and came up
>> with some improvements to bluestore  to make this change have
>> little performance impact (it even increases performance in many
>>  https://github.com/ceph/ceph/pull/34588
>>  https://github.com/ceph/ceph/pull/33434
>>  https://github.com/ceph/ceph/pull/33365
>> On 2/14/21 9:21 AM, Loïc Dachary wrote:
>>> Reading Karan's blog post about benchmarking the insertion of billions
> objects to Ceph via S3 / RGW from last year, it reads:
>>>> we decided to lower bluestore_min_alloc_size_hdd to 18KB and re-test.
> As represented in chart-5, the object creation rate found to be notably
> reduced after lowering the bluestore_min_alloc_size_hdd parameter from
> (default) to 18KB. As such, for objects
larger than the
> bluestore_min_alloc_size_hdd , the default values seems to be optimal,
> smaller objects further require more investigation if you intended to
> reduce bluestore_min_alloc_size_hdd parameter.
>>> There also is a mail thread dated 2018 on this topic as well, with the
> same conclusion although using RADOS directly and not RGW. I read the
> RGW data layout page in the documentation and concluded that by
> every object inserted with S3 / RGW will
indeed use at least 64kb. A
> request from last year seems to confirm it
and also suggests
> bluestore_min_alloc_size_hdd has adverse
>>> That being said, I'm curious to know if people developed strategies to
> cope with this overhead. Someone mentioned packing objects together
> side to make them larger. But maybe there are
simpler ways to do the
>  https://www.redhat.com/en/blog/scaling-ceph-billion-objects-and-beyond
Loïc Dachary, Artisan Logiciel Libre
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