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Posted to user@hbase.apache.org by Gaojinchao <ga...@huawei.com> on 2011/11/26 07:44:16 UTC
A question about dfs.replication.min setting.
When HBase use HDFS system file. How do we set "dfs.replication.min"?
who can share relevant experience?
Currently on our environment, We use the default value:
dfs.replication :3
dfs.replication.min: 1
I found some block lost when the IO is very busy.
Re: A question about dfs.replication.min setting.
Posted by Jahangir Mohammed <md...@gmail.com>.
The setting is available in hdfs-site.xml.
Default replication is 3, the dfs.replication.min is used only when the
namenode is in safe mode i.e. on startup and leaves that state once all
blocks are reported by datanodes.
Thanks,
Jahangir Mohammed
On Sat, Nov 26, 2011 at 1:44 AM, Gaojinchao <ga...@huawei.com> wrote:
> When HBase use HDFS system file. How do we set "dfs.replication.min"?
> who can share relevant experience?
> Currently on our environment, We use the default value:
> dfs.replication :3
> dfs.replication.min: 1
> I found some block lost when the IO is very busy.
>
>
>
>
>
Re: A question about dfs.replication.min setting.
Posted by Harsh J <ha...@cloudera.com>.
You can set it in hbase-site.xml:
http://hbase.apache.org/book.html#hdfs_client_conf
On 26-Nov-2011, at 12:14 PM, Gaojinchao wrote:
> When HBase use HDFS system file. How do we set "dfs.replication.min"?
> who can share relevant experience?
> Currently on our environment, We use the default value:
> dfs.replication :3
> dfs.replication.min: 1
> I found some block lost when the IO is very busy.
>
>
>
>
Re: A question about dfs.replication.min setting.
Posted by Gaojinchao <ga...@huawei.com>.
Thanks for your response.
My case is complicated. It is not the issue of xceivers.
The main reason of asynchronously I/O, When we write some data to an "async" mounted partition(that is default in os), such as "create", "mkdir", "rmdir", "rename" and "write". These operations need a period time to sync. If one machine crashes, will may have some files or some blocks lose. If setting "sync" affects all I/O to the file system (both meta data and file contents), performance is low.
I agree with Harsh, If sets "dfs.replication.min" to 2. It may cause RSes to go down. So I want to know how set the " dfs.replication.min" in production. Who has experience, Whether by increasing the value to increase reliability?
Cheers.
-----邮件原件-----
发件人: Jahangir Mohammed [mailto:md.jahangir27@gmail.com]
发送时间: 2011年11月26日 15:22
收件人: user@hbase.apache.org
主题: Re: A question about dfs.replication.min setting.
Since you say you see blocks loosing when it's IO busy/bound, I very much
that think the xceivers has been set to low value. Raise its value.
Thanks,
Jahangir Mohammed.
On Sat, Nov 26, 2011 at 2:21 AM, Jahangir Mohammed
<md...@gmail.com>wrote:
> What is dfs.datanode.max.xceivers set?
>
>
>
> On Sat, Nov 26, 2011 at 2:17 AM, Harsh J <ha...@cloudera.com> wrote:
>
>> Ah wait, my bad. Do not raise dfs.replication.min when using HBase - it
>> can cause RSes to go down if min block #s > 1 were not completely
>> guaranteed. As a result, close() on files fail to work and block out until
>> the replicas are available to satisfy dfs.replication.min - and thereby
>> cause things to timeout/fail.
>>
>> (Think the problem is to do with use of sync, but am not sure yet --
>> general writes work properly with that config, by retrying enough times to
>> get locations).
>>
>> On 26-Nov-2011, at 12:14 PM, Gaojinchao wrote:
>>
>> > When HBase use HDFS system file. How do we set "dfs.replication.min"?
>> > who can share relevant experience?
>> > Currently on our environment, We use the default value:
>> > dfs.replication :3
>> > dfs.replication.min: 1
>> > I found some block lost when the IO is very busy.
>> >
>> >
>> >
>> >
>>
>>
>
Re: A question about dfs.replication.min setting.
Posted by Jahangir Mohammed <md...@gmail.com>.
Since you say you see blocks loosing when it's IO busy/bound, I very much
that think the xceivers has been set to low value. Raise its value.
Thanks,
Jahangir Mohammed.
On Sat, Nov 26, 2011 at 2:21 AM, Jahangir Mohammed
<md...@gmail.com>wrote:
> What is dfs.datanode.max.xceivers set?
>
>
>
> On Sat, Nov 26, 2011 at 2:17 AM, Harsh J <ha...@cloudera.com> wrote:
>
>> Ah wait, my bad. Do not raise dfs.replication.min when using HBase - it
>> can cause RSes to go down if min block #s > 1 were not completely
>> guaranteed. As a result, close() on files fail to work and block out until
>> the replicas are available to satisfy dfs.replication.min - and thereby
>> cause things to timeout/fail.
>>
>> (Think the problem is to do with use of sync, but am not sure yet --
>> general writes work properly with that config, by retrying enough times to
>> get locations).
>>
>> On 26-Nov-2011, at 12:14 PM, Gaojinchao wrote:
>>
>> > When HBase use HDFS system file. How do we set "dfs.replication.min"?
>> > who can share relevant experience?
>> > Currently on our environment, We use the default value:
>> > dfs.replication :3
>> > dfs.replication.min: 1
>> > I found some block lost when the IO is very busy.
>> >
>> >
>> >
>> >
>>
>>
>
Re: A question about dfs.replication.min setting.
Posted by Jahangir Mohammed <md...@gmail.com>.
What is dfs.datanode.max.xceivers set?
On Sat, Nov 26, 2011 at 2:17 AM, Harsh J <ha...@cloudera.com> wrote:
> Ah wait, my bad. Do not raise dfs.replication.min when using HBase - it
> can cause RSes to go down if min block #s > 1 were not completely
> guaranteed. As a result, close() on files fail to work and block out until
> the replicas are available to satisfy dfs.replication.min - and thereby
> cause things to timeout/fail.
>
> (Think the problem is to do with use of sync, but am not sure yet --
> general writes work properly with that config, by retrying enough times to
> get locations).
>
> On 26-Nov-2011, at 12:14 PM, Gaojinchao wrote:
>
> > When HBase use HDFS system file. How do we set "dfs.replication.min"?
> > who can share relevant experience?
> > Currently on our environment, We use the default value:
> > dfs.replication :3
> > dfs.replication.min: 1
> > I found some block lost when the IO is very busy.
> >
> >
> >
> >
>
>
Re: A question about dfs.replication.min setting.
Posted by Harsh J <ha...@cloudera.com>.
Ah wait, my bad. Do not raise dfs.replication.min when using HBase - it can cause RSes to go down if min block #s > 1 were not completely guaranteed. As a result, close() on files fail to work and block out until the replicas are available to satisfy dfs.replication.min - and thereby cause things to timeout/fail.
(Think the problem is to do with use of sync, but am not sure yet -- general writes work properly with that config, by retrying enough times to get locations).
On 26-Nov-2011, at 12:14 PM, Gaojinchao wrote:
> When HBase use HDFS system file. How do we set "dfs.replication.min"?
> who can share relevant experience?
> Currently on our environment, We use the default value:
> dfs.replication :3
> dfs.replication.min: 1
> I found some block lost when the IO is very busy.
>
>
>
>