[Gluster-users] Access data directly from underlying storage

[Rumen Telbizov]

Hello everyone,

I am curious to know other people's experience with reading data straight
from the underlying volume. According to the documentation it should be
fine:

http://www.gluster.org/documentation/Technical_FAQ/

*Can I directly access the data on the underlying storage volumes?*
>
> If you are just doing just read()/access()/stat() like operations, you
> should be fine. If you are not using any new features (like
> quota/geo-replication etc etc) then technically, you can modify (but surely
> not rename(2) and link(2)) the data inside.
>
> Note that this is not tested as part of gluster’s release cycle and not
> recommended for production use.
>

The last sentence doesn't recommend it for production use. I was wondering
if there's any other concern besides the fact that it's not tested as part
of the release cycle or one could expect actual some problems with the data
being read while doing so?

What I am interested is *only* read operations (readdir, stat, read data).
All the write operations will continue going over the shared/mounted drive.
So what I want to know is that the data that I am reading will be
consistent with the rest of the bricks and not corrupted in any way.

The reason why I am looking into this is two-fold:
1. I have a lot of small files (hundreds of thousands) that need to be read
and reread very frequently. Doing so directly from the underlying disk is
way faster.
2. Once I've read them once both metadata and actual data is automatically
cached in the OS filesystem cache, thus subsequent reads take almost no
time since very few of those files actually change between reruns.

I run a three (or five) way mirror and nothing fancy (no geo and such) so
if I could, I would prefer to read of the local disk​ but I want to be
certain that those reads, in terms of correctness and consistency, will be
equivalent to reading of the shared drive itself.

​Thank you in advance for sharing your experience.​

Regards,
-- 
Rumen Telbizov
Unix Systems Administrator <http://telbizov.com>
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