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From "donhoff_h" <165612...@qq.com>
Subject 回复: BucketCache Configuration Problem
Date Tue, 03 Mar 2015 02:54:26 GMT
Hi, Stack

Thanks very much for your quick reply.    

It's OK to tell you my app sinario. I am not sure if it is very extreme. :)

Recently we consider using HBase to store all the pictures of our bank. For example , the
pictures from loan apply & contract, credit card apply, draft etc. Usually the total count
of pictures that the business users will access daily is not very high. But since each picture
takes a lot of space, the total amount of pictures that business users will access daily is
very high. So we considing using cache to improve the performance. 

Since the total space daily accessed is very large and the memory may not contain so much
space, we consider use "FILE" instead of "offheap" for the BucketCache. At this situation
if we use CBC policy, it will lead to that the memory will only cache the meta blocks and
leave the datablocks stored in "FILE'. And it seems the memory is not taking full usage, because
the total count of pictures daily accessed is not very high and we may not need to cache many
meta blocks. So we want to know if the RAW L1+L2 is better. Maybe it can take full use of
memory and meanwhile cache a lot of datablocks. That's the reason why I tried to setup a RAW
L1+L2 configuration.

By the way, I tried your advice to set hbase.bucketcache.combinedcache.enabled=fales. But
the WebUI of the regionserver said that I did not deploy L2 cache. You can see it in the attachement.
Is that still caused by my HBase Version?  Is RAW L1+L2 only applicable in HBase1.0?

At last, you said that the refguide still needs to be maintained. I totally understand.  :)
It is the same in my bank. We also have a lot of docs that need to be updated. And I shall
be very glad if my questions can help you to find those locations and can help others.

Thanks again!‍




------------------ 原始邮件 ------------------
发件人: "Stack";<stack@duboce.net>;
发送时间: 2015年3月3日(星期二) 凌晨0:13
收件人: "Hbase-User"<user@hbase.apache.org>; 

主题: Re: BucketCache Configuration Problem



On Mon, Mar 2, 2015 at 6:19 AM, donhoff_h <165612158@qq.com> wrote:

> Hi, Stack
>
> Thanks for your reply and also thanks very much for your reply to my
> previous mail "Questions about BucketCache".
>
> The hbase.bucketcache.bucket.sizes property takes effect. I did not notice
> that in your first mail you have told me the name should be
> hbase.bucketcache.bucket.sizes, instead of hbase.bucketcache.sizes. I
> noticed this point until your last mail. It's my fault. Thanks for your
> patient.
>
>
No harm. Thanks for your patience and writing the list.



> As to the relationship between HBASE_OFFHEAPSIZE and
> -XX:MaxDirectMemorySize, I followed your advice to find in the bin/hbase
> the statements that contain HBASE_OFFHEAPSIZE, but I found that there isn't
> any statement which contains HBASE_OFFHEAPSIZE. I also tried
> "bin/hbase-daemon.sh" and "bin/hbase-config.sh", they don't contain
> HBASE_OFFHEAPSIZE either. So I still don't know their relationship. My
> HBase version is 0.98.10. Is HBASE_OFFHEAPSIZE not used in this version ?
>
>
This is my fault. The above applies to versions beyond 0.98, not your
version. Please pass MaxDirectMemorySize inside HBASE_OPTS.




> As to "the pure secondary cache" or "bypass CBC", I mean use BucketCache
> as a strict L2 cache to the L1 LruBlockCache, ie the Raw L1+L2. The point
> comes from the reference guide of Apache HBase, which says : "It is
> possible to deploy an L1+L2 setup where we bypass the CombinedBlockCache
> policy and have BucketCache working as a strict L2 cache to the L1
> LruBlockCache. For such a setup, set CacheConfig.BUCKET_CACHE_COMBINED_KEY
> to false. In this mode, on eviction from L1, blocks go to L2. When a block
> is cached, it is cached first in L1. When we go to look for a cached block,
> we look first in L1 and if none found, then search L2. Let us call this
> deploy format, Raw L1+L2."
> I want to configure this kind of cache not because the CBC poliy is not
> good, but because I am a tech-leader in a bank. I need to compare these two
> kinds of cache to make a decision for our differenct kinds of apps. The
> reference guide said I can configure in
> "CacheConfig.BUCKET_CACHE_COMBINED_KEY‍", but is there anyway I can
> configure in hbase-site.xml?
>
>
I see.

BUCKET_CACHE_COMBINED_KEY == hbase.bucketcache.combinedcache.enabled.  Set
it to false in your hbase-site.xml.

But lets backup and let me save you some work. Such an 'option' should be
struck from the refguide as an exotic permutation that only in the most
extreme of cases would perform better than CBC. Do you have a loading where
you think this combination would be better suited? If so, would you mind
telling us of it?

Meantime, we need to work on posting different versions of our doc so
others don't have the difficult time you have had above. We've been lazy up
to this because the doc was generally applicable but bucketcache is one of
the locations where version matters.

Yours,
St.Ack






> Many Thanks!‍
>
>
>
>
> ------------------ 原始邮件 ------------------
> 发件人: "Stack";<stack@duboce.net>;
> 发送时间: 2015年3月2日(星期一) 下午2:30
> 收件人: "Hbase-User"<user@hbase.apache.org>;
>
> 主题: Re: BucketCache Configuration Problem
>
>
>
> On Sun, Mar 1, 2015 at 12:57 AM, donhoff_h <165612158@qq.com> wrote:
>
> > Hi, experts
> >
> > I am using HBase0.98.10 and have 3 problems about BucketCache
> > configuration.
> >
> > First:
> > I  read the reference guide of Apache HBase to learn how to config
> > BucketCache. I find that when using offheap BucketCache, the reference
> > guide says that I should config the HBASE_OFFHEAPSIZE , it also says
> that
> > I should config -XX:MaxDirectMemorySize. Since these two parameters  are
> > both related to the DirectMemory, I am confused which one should I
> > configure?
> >
> >
> See bin/hbase how HBASE_OFFHEAPSIZE gets interpolated as value of the
> -XX:MaxDirectMemorySize passed to java (so set HBASE_OFFHEAPSIZE) (will fix
> the doc so more clear)
>
>
>
> > Second:
> > I want to know how to configure the  BucketCache as a pure secondary
> > cache, which I mean to bypass the  CombinedBlockCache policy. I tried to
> > configure as following , but when I  go to the regionserver's webUI, I
> > found it says "No L2 deployed"
> >
> > hbase.bucketcache.ioengine=offheap
> > hbase.bucketcache.size=200
> > hbase.bucketcache.combinedcache.enabled=false
> >
> >
> What do you mean by pure secondary cache? Which block types do you want in
> the bucketcache?
>
> Why bypass CBC? We've been trying to simplify bucketcache deploy. Part of
> this streamlining has been removing the myriad options because they tend to
> confuse and give user a few simple choices. Do the options not work for
> you?
>
>
>
> > Third:
> > I  made the following configuration to set the Bucket Sizes. But from
> > regionserver's WebUI, I found that (4+1)K and (8+1)K sizes are used,
> > (64+1)K sizes are not used. What's wrong with my configuration?
> > hbase.bucketcache.ioengine=offheap
> > hbase.bucketcache.size=200
> > hbase.bucketcache.combinedcache.enabled=true
> > hbase.bucketcache.sizes=65536  hfile.block.cache.sizes=65536 I configured
> > these two both for I don't  know which one is in use now.
> >
> >
> As per previous mail (and HBASE-13125), hfile.block.cache.sizes has no
> effect in 0.98.x.  Also per our previous mail "Questions about
> BucketCache", isn't it hbase.bucketcache.bucket.sizes that you want?
>
> You have tried the defaults and they do not fit your access patten?
>
> Yours,
> St.Ack
>
>
> > Many Thanks!‍
>
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