[Gluster-users] Performance

[Mohit Anchlia]

I am not sure how valid this performance url is

http://www.gluster.com/community/documentation/index.php/Guide_to_Optimizing_GlusterFS

Does it make sense to separate out the journal and create mkfs -I 256?

Also, if I already have a file system on a different partition can I
still use it to store journal from other partition without corrupting
the file system?

On Thu, Apr 21, 2011 at 7:23 PM, Joe Landman
<landman at scalableinformatics.com> wrote:
> On 04/21/2011 08:49 PM, Mohit Anchlia wrote:
>>
>> After lot of digging today finaly figured out that it's not really
>> using PERC controller but some Fusion MPT. Then it wasn't clear which
>
> PERC is a rebadged LSI based on the 1068E chip.
>
>> tool it supports. Finally I installed lsiutil and was able to change
>> the cache size.
>>
>> [root at dsdb1 ~]# lspci|grep LSI
>> 02:00.0 SCSI storage controller: LSI Logic / Symbios Logic SAS1068E
>> PCI-Express Fusion-MPT SAS (rev 08)
>
>  This looks like PERC.  These are roughly equivalent to the LSI 3081 series.
>  These are not fast units.  There is a variant of this that does RAID6, its
> usually available as a software update or plugin module (button?) to this.
>  I might be thinking of the 1078 chip though.
>
>  Regardless, these are fairly old designs.
>
>
>> [root at dsdb1 ~]# dd if=/dev/zero of=/data/big.file bs=128k count=40k
>> oflag=direct
>> 1024+0 records in
>> 1024+0 records out
>> 134217728 bytes (134 MB) copied, 0.742517 seconds, 181 MB/s
>>
>> I compared this with SW RAID mdadm that I created yesterday on one of
>> the servers and I get around 300MB/s. I will test out first with what
>> we have before destroying and testing with mdadm.
>
> So the software RAID is giving you 300 MB/s and the hardware 'RAID' is
> giving you ~181 MB/s?  Seems a pretty simple choice :)
>
> BTW: The 300MB/s could also be a limitation of the PCIe channel interconnect
> (or worse, if they hung the chip off a PCIx bridge).  The motherboard
> vendors are generally loathe to put more than a few PCIe lanes for handling
> SATA, Networking, etc.  So typically you wind up with very low powered
> 'RAID' and 'SATA/SAS' on the motherboard, connected by PCIe x2 or x4 at
> most.  A number of motherboards have NICs that are served by a single PCIe
> x1 link.
>
>> Thanks for your help that led me to this path. Another question I had
>> was when creating mdadm RAID does it make sense to use multipathing?
>
> Well, for a shared backend over a fabric, I'd say possibly.  For an internal
> connected set, I'd say no.  Given what you are doing with Gluster, I'd say
> that the additional expense/pain of setting up a multipath scenario probably
> isn't worth it.
>
> Gluster lets you get many of these benefits at a higher level in the stack.
>  Which to a degree, and in some use cases, obviates the need for
> multipathing at a lower level.  I'd still suggest real RAID at the lower
> level (RAID6, and sometimes RAID10 make the most sense) for the backing
> store.
>
>
> --
> Joseph Landman, Ph.D
> Founder and CEO
> Scalable Informatics, Inc.
> email: landman at scalableinformatics.com
> web  : http://scalableinformatics.com
>       http://scalableinformatics.com/sicluster
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>