[Gluster-users] Gluster performance on the small files

[Joe Julian]

On 02/12/2015 10:58 PM, Punit Dambiwal wrote:
> Hi,
>
> I have seen the gluster performance is dead slow on the small 
> files...even i am using the SSD....it's too bad performance....even i 
> am getting better performance in my SAN with normal SATA disk...
>
> I am using distributed replicated glusterfs with replica count=2...i 
> have all SSD disks on the brick...
>
> root at vm3:~# dd bs=64k count=4k if=/dev/zero of=test oflag=dsync
>
> 4096+0 records in
>
> 4096+0 records out
>
> 268435456 bytes (268 MB) copied, 57.3145 s, 4.7 MB/s
>
>
> root at vm3:~# dd bs=64k count=4k if=/dev/zero of=test conv=fdatasync
>
> 4096+0 records in
>
> 4096+0 records out
>
> 268435456 bytes (268 MB) copied, 1.80093 s, 149 MB/s
>
>
>
How small is your VM image? The image is the file that GlusterFS is 
serving, not the small files within it. Perhaps the filesystem you're 
using within your VM is inefficient with regard to how it handles disk 
writes.

I believe your concept of "small file" performance is misunderstood, as 
is often the case with this phrase. The "small file" issue has to do 
with the overhead of finding and checking the validity of any file, but 
with a small file the percentage of time doing those checks is 
proportionally greater. With your VM image, that file is already open. 
There are no self-heal checks or lookups that are happening in your 
tests, so that overhead is not the problem.
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