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From Mikhail Antonov <olorinb...@gmail.com>
Subject Re: HBase as a file repository
Date Tue, 04 Apr 2017 19:44:01 GMT
Unfamiliar with MOB codebase but reading.. " It takes 100 ms
to retrieve a 1MB cell (file), and only after retrieving I am able to start
serving it to the end user".. Is that avg, p90, p99?

Do we have htrace probes on that codepath? Do we do more seeks that we
expect?

-Mikhail

On Tue, Apr 4, 2017 at 11:23 AM, Stack <stack@duboce.net> wrote:

> On Thu, Mar 30, 2017 at 9:25 PM, Daniel Jeliński <djelinski1@gmail.com>
> wrote:
>
> > Thank you Ted for your response.
> >
> > I have read that part of HBase book. It never explained why objects over
> > 10MB are no good, and did not suggest an alternative storage medium for
> > these.
> >
> >
> Thats a hole. I filed HBASE-17875.
>
> The 10MB upper-bound is a conservative upper bound. Bigger Cells will skirt
> buffer pools so we'll do one-off allocations per read. The GC will
> experience a shock, and so on.
>
>
> > I have also read this:
> > http://hbase.apache.org/book.html#regionserver_sizing_rules_of_thumb
> > And yet I'm trying to put 36TB on a machine. I certainly hope that the
> > number of region servers is the only real limiter to this.
> >
> >
> In the refguide, the guidance is intentionally conservative. It is probably
> also stale at this point. Most users/devs do not do the degree of PoC'ing
> that you have. The recommendations are more for the latter than you.
>
>  ...
>
>
> > I checked async HBase projects, but apparently they're focused on running
> > the requests in background, rather than returning results earlier. HBase
> > streaming on Google returns just references to Spark.
> >
> > HBase JIRA has a few apparently related issues:
> > https://issues.apache.org/jira/browse/HBASE-17721 is pretty fresh with
> no
> > development yet, and https://issues.apache.org/jira/browse/HBASE-13467
> > seems to have died already.
> >
> >
> I pinged on HBASE-13467. My understanding was that this project was
> underway...
>
> St.Ack
>
>
>
>
> > I captured the network traffic between the client and the region server
> > when I requested one cell, and writing a custom client seems easy enough.
> > Are there any reasons other than the API that justify the 10MB limit on
> > MOBs?
> > Thanks,
> > Daniel
> >
> >
> >
> > 2017-03-31 0:03 GMT+02:00 Ted Yu <yuzhihong@gmail.com>:
> >
> > > Have you read:
> > > http://hbase.apache.org/book.html#hbase_mob
> > >
> > > In particular:
> > >
> > > When using MOBs, ideally your objects will be between 100KB and 10MB
> > >
> > > Cheers
> > >
> > > On Thu, Mar 30, 2017 at 1:01 PM, Daniel Jeliński <djelinski1@gmail.com
> >
> > > wrote:
> > >
> > > > Hello,
> > > > I'm evaluating HBase as a cheaper replacement for NAS as a file
> storage
> > > > medium. To that end I have a cluster of 5 machines, 36TB HDD each;
> I'm
> > > > planning to initially store ~240 million files of size 1KB-100MB,
> total
> > > > size 30TB. Currently I'm storing each file under an individual
> column,
> > > and
> > > > I group related documents in the same row. The files from the same
> row
> > > will
> > > > be served one at a time, but updated/deleted together.
> > > >
> > > > Loading the data to the cluster went pretty well; I enabled MOB on
> the
> > > > table and have ~50 regions per machine. Writes to the table are done
> by
> > > an
> > > > automated process, and cluster's performance in that area is more
> than
> > > > sufficient. On the other hand, reads are interactive, as the files
> are
> > > > served to human users over HTTP.
> > > >
> > > > Now. HBase Get in Java API is an atomic operation in the sense that
> it
> > > does
> > > > not complete until all data is retrieved from the server. It takes
> 100
> > ms
> > > > to retrieve a 1MB cell (file), and only after retrieving I am able to
> > > start
> > > > serving it to the end user. For larger cells the wait time is even
> > > longer,
> > > > and response times longer than 100 ms are bad for user experience. I
> > > would
> > > > like to start streaming the file over HTTP as soon as possible.
> > > >
> > > > What's the recommended approach to avoid or reduce the delay between
> > when
> > > > HBase starts sending the response and when the application can act on
> > it?
> > > > Thanks,
> > > > Daniel
> > > >
> > >
> >
>



-- 
Thanks,
Michael Antonov

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