[ceph-users] BlueStore questions about workflow and performance

Mark Nelson mnelson at redhat.com
Tue Oct 3 06:16:24 PDT 2017



On 10/03/2017 07:59 AM, Alex Gorbachev wrote:
> Hi Sam,
>
> On Mon, Oct 2, 2017 at 6:01 PM Sam Huracan <nowitzki.sammy at gmail.com
> <mailto:nowitzki.sammy at gmail.com>> wrote:
>
>     Anyone can help me?
>
>     On Oct 2, 2017 17:56, "Sam Huracan" <nowitzki.sammy at gmail.com
>     <mailto:nowitzki.sammy at gmail.com>> wrote:
>
>         Hi,
>
>         I'm reading this document:
>          http://storageconference.us/2017/Presentations/CephObjectStore-slides.pdf
>
>         I have 3 questions:
>
>         1. BlueStore writes both data (to raw block device) and metadata
>         (to RockDB) simultaneously, or sequentially?
>
>         2. From my opinion, performance of BlueStore can not compare to
>         FileStore using SSD Journal, because performance of raw disk is
>         less than using buffer. (this is buffer purpose). How do you think?
>
>         3.  Do setting Rock DB and Rock DB Wal in SSD only enhance
>         write, read performance? or both?
>
>         Hope your answer,
>
>
> I am researching the same thing, but recommend you look
> at http://ceph.com/community/new-luminous-bluestore
>
> And also search for Bluestore cache to answer some questions.  My test
> Luminous cluster so far is not as performant as I would like, but I have
> not yet put a serious effort into tuning it, amd it does seem stable.
>
> Hth, Alex

Hi Alex,

If you see anything specific please let us know.  There are a couple of 
corner cases where bluestore is likely to be slower than filestore 
(specifically small sequential reads/writes with no client side cache or 
read ahead).  I've also seen some cases where filestore has higher read 
throughput potential (4MB seq reads with multiple NVMe drives per OSD 
node).  In many other cases bluestore is faster (and sometimes much 
faster) than filestore in our tests.  Writes in general tend to be 
faster and high volume object creation is much faster with much lower 
tail latencies (filestore really suffers in this test due to PG splitting).

Mark

>
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> --
> --
> Alex Gorbachev
> Storcium
>
>
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