[Gluster-devel] Full bore.

Chris Johnson johnson at nmr.mgh.harvard.edu
Thu Nov 15 17:56:05 UTC 2007

On Thu, 15 Nov 2007, Kevan Benson wrote:

> Chris Johnson wrote:
>>      Hi again,
>>      Ok, now have CentOS5 on the two DELL front ends to this SATA
>> Beast thingy.  I have gluster enhanced fuse on both and glusterfs
>> 1.3.5 on both.
>>      Performance is still way below NFS.  I have turned on
>> write-behind and read-ahead.  And with fuse it's a little faster. but
>> not significantly.  To get more out of this it's pretty ovious I need
>> to do unify if I want BIG space, maybe striping.  If I  want high
>> availability I need AFR (that works with unify?).  And if I want to
>> use the second DELL front end I'm probably going to need locking if
>> they share drives.  Self healing works, right?  Wasn't there discussion
>> about a potential problem not long ago?
>>       Sound about right?
> Pretty much.  The self heal discussion was about edge cases.  It works for 
> most situations you'll see it in.
> AFR and Unify (and striping) are stackable, layer as many as you want (AFR 
> dual unified AFR's if you want.

      I might if I get another one.

>>       I think I'm seeing from the glusterfs wiki that the order
>> in which things are defined in the config files matters.  It's a bit
>> unclear to me what the real order of things should be.
> It's doesn't REALLY matter too much, unless it's a client config and you 
> aren't explicitly defining the share to load (then it grabs the last 
> specified).
> Most translators specified that rely on other volumes have you specifically 
> state which volumes they are using.  The only way I see order mattering there 
> is that the subvolumes used by a translator may need to be defined above the 
> location they are used in a translator. I.e. define share1 and share2 before 
> you include them in an AFR/Unify. I'm not sure this is required, but it's 
> probably easier to read the configs if you do it anyways.

      About what I thought but the wiki sounded otherwise.

>>      Oh, this is ext3 with xattr turned on.  But we could use Reiserfs
>> if that would help.  I may run tests on that as well.
> I don't know about others, but I wouldn't use reiserfs if you care about your 
> data and aren't supplying redundancy above teh file system level (with 
> glusterfs, for example).  I've seen multiple reports of how Reiserfs has a 
> tendency to have unrecoverable errors in the file system when it gets 
> sufficiently screwed up, basically necessitating a reformat of the partition.

      Huh.  Now that's interesting.  We've been running our mail server
off Reiserfs for a few years now and never an issue.  It's servived
power outs and dropped drives.  We're using software RAID on it.

>>      Can we have a discussion on whether I'm heading in the right
>> direction and what order things go in for the config files?
> That depends on your goals.  What's important here, speed, redundancy, or a 
> mix of both?

       Both of course.  Are the mutually exclusive?  Please, I know
they can be to some extent.  I'm talking about the real world,
whatever that is.  I need to get the performance up,
redundancy/failover would be be real good too.  NFS has a few problems
with that.

>>      Also, any operational notes on running gluster on anything this
>> big will be appreciated.
> -- 
> -Kevan Benson
> -A-1 Networks

Chris Johnson               |Internet: johnson at nmr.mgh.harvard.edu
Systems Administrator       |Web:      http://www.nmr.mgh.harvard.edu/~johnson
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