Where to put the journal

Where to put the journal

[Xuân Baldauf]

Hello,

I want to setup a Linux software RAID 5 over disks of different speed 
with reiserfs on top. I know that the journal has to be accessed 
frequently for comparably small accesses. That's why I'm considering to 
"offload" the journal onto an extra partition on a faster disk of the 
RAID set.

Thus, the journal would not be protected by the RAID, but this is not so 
important for me.

Is this kind of reasoning sane? Would there be any speedup by offloading 
the journal?

Thanks,

Xuân Baldauf.

Re: Where to put the journal

[Vladimir V. Saveliev]

Hello

Xuân Baldauf wrote:
> Hello,
> 
> I want to setup a Linux software RAID 5 over disks of different speed 
> with reiserfs on top. I know that the journal has to be accessed 
> frequently for comparably small accesses. That's why I'm considering to 
> "offload" the journal onto an extra partition on a faster disk of the 
> RAID set.
> 
> Thus, the journal would not be protected by the RAID, but this is not so 
> important for me.
> 
> Is this kind of reasoning sane? Would there be any speedup by offloading 
> the journal?
> 

Person who did some tests on non standard journal is on vacation. He is expected to come back today. Maybe he remembers benchmark results,

Re: Where to put the journal

[Edward Shishkin]

Vladimir V. Saveliev wrote:

> Hello
>
> Xuân Baldauf wrote:
>
>> Hello,
>>
>> I want to setup a Linux software RAID 5 over disks of different speed 
>> with reiserfs on top. I know that the journal has to be accessed 
>> frequently for comparably small accesses. That's why I'm considering 
>> to "offload" the journal onto an extra partition on a faster disk of 
>> the RAID set.
>>
>> Thus, the journal would not be protected by the RAID, but this is not 
>> so important for me.
>>
>> Is this kind of reasoning sane? Would there be any speedup by 
>> offloading the journal?
>>
>

Hello.
Unfortunately comprehensive results of journal relocation are obsolete
as it was done at the beginning of mongo evolution. As I remember there
were no any essential speedups. The only result of  journal  relocation that
was created by new mongo benchmark can be found here:
http://thebsh.namesys.com/benchmarks/journal_relocation_to_NVRAM.html

Edward.

> Person who did some tests on non standard journal is on vacation. He 
> is expected to come back today. Maybe he remembers benchmark results,
>
>
>

Re: Where to put the journal

[Xuân Baldauf]

Edward Shishkin wrote:

> Vladimir V. Saveliev wrote:
>
>> Hello
>>
>> Xuân Baldauf wrote:
>>
>>> Hello,
>>>
>>> I want to setup a Linux software RAID 5 over disks of different 
>>> speed with reiserfs on top. I know that the journal has to be 
>>> accessed frequently for comparably small accesses. That's why I'm 
>>> considering to "offload" the journal onto an extra partition on a 
>>> faster disk of the RAID set.
>>>
>>> Thus, the journal would not be protected by the RAID, but this is 
>>> not so important for me.
>>>
>>> Is this kind of reasoning sane? Would there be any speedup by 
>>> offloading the journal?
>>>
>>
>
> Hello.
> Unfortunately comprehensive results of journal relocation are obsolete
> as it was done at the beginning of mongo evolution. As I remember there
> were no any essential speedups. The only result of  journal  
> relocation that
> was created by new mongo benchmark can be found here:
> http://thebsh.namesys.com/benchmarks/journal_relocation_to_NVRAM.html

Thank you,

essentially, these numbers say that relocation provided a speedup of 
about 10% for write. This surprises me a bit, because I expected a 
significantly smaller seek count for a write operation. Nevertheless, 
maybe I should run benchmarks with many small files for myself. :-)

>
> Edward.


ciao,

Xuân Baldauf.

>
>> Person who did some tests on non standard journal is on vacation. He 
>> is expected to come back today. Maybe he remembers benchmark results,
>

Re: Where to put the journal

[Edward Shishkin]

Xuân Baldauf wrote:

> Edward Shishkin wrote:
>
>> Vladimir V. Saveliev wrote:
>>
>>> Hello
>>>
>>> Xuân Baldauf wrote:
>>>
>>>> Hello,
>>>>
>>>> I want to setup a Linux software RAID 5 over disks of different 
>>>> speed with reiserfs on top. I know that the journal has to be 
>>>> accessed frequently for comparably small accesses. That's why I'm 
>>>> considering to "offload" the journal onto an extra partition on a 
>>>> faster disk of the RAID set.
>>>>
>>>> Thus, the journal would not be protected by the RAID, but this is 
>>>> not so important for me.
>>>>
>>>> Is this kind of reasoning sane? Would there be any speedup by 
>>>> offloading the journal?
>>>>
>>>
>>
>> Hello.
>> Unfortunately comprehensive results of journal relocation are obsolete
>> as it was done at the beginning of mongo evolution. As I remember there
>> were no any essential speedups. The only result of  journal  
>> relocation that
>> was created by new mongo benchmark can be found here:
>> http://thebsh.namesys.com/benchmarks/journal_relocation_to_NVRAM.html
>
>
> Thank you,
>
> essentially, these numbers say that relocation provided a speedup of 
> about 10% for write. 


Note this is for data logging journal mode (mount option "data=journal")
Edward.

> This surprises me a bit, because I expected a significantly smaller 
> seek count for a write operation. Nevertheless, maybe I should run 
> benchmarks with many small files for myself. :-)
>
>>
>> Edward.
>
>
>
> ciao,
>
> Xuân Baldauf.
>
>>
>>> Person who did some tests on non standard journal is on vacation. He 
>>> is expected to come back today. Maybe he remembers benchmark results,
>>
>>
>
>
>