[Gluster-users] Fwd: Very slow performance when enabling tierd storage with SSD

[Benjamin Kingston]

Hello Rafi,

Thanks for the reply please see my answers below

On Sat, Sep 3, 2016 at 12:07 AM, Mohammed Rafi K C <rkavunga at redhat.com>
wrote:

> Hi Benjamin,
>
>
> Can you tell us more about your work-load like the file size
>
Files are a range from 10GB test file generated from /dev/urandom, many
100MB folder separated files to smaller images and text files
This is a lab so typically there is no load, in the case of my testing this
issue the only file being accessed was the 10GB test file.

> , size of both hot and cold storage
>
Hot storage is a 315GB portion of a 512GB SSD
Cold storage is a replica made up of 3 bricks on two nodes. totaling 17TB

> how the files are created (after attaching the tier or before attaching
> the tier)
>
I've experienced performance issues with files created before hot
attachment, 10GB test file, and copying files to the volume after
attachment (100MB files)

> , how long have you been using the tier volume, etc.
>
At the moment I am not using the hot tier after discovering the performance
loss. I originally turned on after learning of the feature a month or so
ago. I feel like I may have actually had this issue since then because I
have been troubleshooting a network throughalput issue since then that was
contributing to a 4MB/s write to the volume. I recently resolved that issue
and the 4MB/s write was still observed until I removed the hot tier.

Unfortunate timing on both issues.

>
> Regards
>
> Rafi KC
>
>
>
>
> On 09/03/2016 09:16 AM, Benjamin Kingston wrote:
>
> Hello all,
>
> I've discovered an issue in my lab that went unnoticed until recently, or
> just came about with the latest Centos release.
>
> When the SSD hot tier is enabled read from the volume is 2MB/s, after
> detaching AND committing, read of the same file is at 150MB/s to /dev/null
>
> If I copy the file to the hot bricks directly the write is 150MB/s and
> read is 500MB/s on the first read, and then 4GB/s on the subsequent reads
> (filesystem RAM caching) to /dev/null
>
> Just enabling tier storage takes the performance to ~10-20IOPS and
> 2-10MB/s even for local node mounted volume.
>
> I don't see any major log issues and I detached and did a fix-layout, but
> it persists when re-enabling the tier.
>
>
>
>
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