[Gluster-devel] GlusterFS Example

Tue Jul 31 02:57:34 UTC 2007

>Client unifies S1 and S2 (call him U1)
>Client unifies S3 and S4 (call him U2)
>Client then AFR's together U1 and U2 and S5
>
>In this example, if I save a file and its *:3, it will appear....
>* on U1 (either S1 or S2 depending on scheduler)
>* on U2 (either S3 or S4 depending on sched.)
>* on S5

Is that supported? I was trying to do something similiar earlier, but was 
told that
AFR is under(is a subvolume of) unify since I was having too many problems. 
Can I create
a couple unifies, and then have both U1 and U2 as subvolumes of AFR? If so, 
let me
know, and I can test it.

Can I do something like the following?
BrickS1-1
BrickS1-2
Unify US1
   subvolumes S1-1,S1-2
BrickS2-1
BrickS2-2
Unify US2
   subvolumes S2-1,S2-2
AFR
  subvolumes US1, US2
  replicate *:2

>From: Matt Paine <matt at mattsoftware.com>
>To: gluster-devel at nongnu.org
>Subject: Re: [Gluster-devel] GlusterFS Example
>Date: Tue, 31 Jul 2007 09:15:32 +1000
>
>
>>>
>>>option replicate *.tmp:1,*.html:4,*.php:4,*.db:1,*:2
>>>
>>>In this case any .tmp or .db files will not get replicated (will sit on
>>>the first afr brick only), all html and php files will be mirrored
>>>across the first four bricks of afr, and all other files will be
>>>mirrorred across the first two bricks. (note all on one line, note comma
>>>delimited, note also no spaces before or after the comma).
>>
>>
>>Right, but is it possible to just tell the config you want to store 2
>>copies of everything without telling each system where the redundant
>>copies should be stored? I.E. I am looking for something like RAID 6,
>>where I have say 8 bricks with two copies of every file. If I just enter
>>*:2 then the spare copies will just be on the first two bricks and since
>>each 8 brick has the same amount of storage I will run out of space on the
>>first two before the others vs the redundant copies distributed over the 8
>>bricks.
>
>
>Absolutly, except its there is a bit more work to do. AFR works by starting 
>at the first brick and any replicating goes to the second, third etc as 
>described above. But these are normal gluster bricks, so there is nothing 
>stopping you from creating an AFR for the first brick, and AFR for the 
>second, and just a posix brick for the rest (if thats what you want of 
>course). Let me try to explain.....
>
>
>Server one has one brick: S1
>Server two has one brick: S2
>Server three has one brick: S3
>Server four has one brick: S4
>Server five has one brick: S5
>
>Client unifies S1 and S2 (call him U1)
>Client unifies S3 and S4 (call him U2)
>Client then AFR's together U1 and U2 and S5
>
>In this example, if I save a file and its *:3, it will appear....
>* on U1 (either S1 or S2 depending on scheduler)
>* on U2 (either S3 or S4 depending on sched.)
>* on S5
>
>If I save a file as only *:1, it will appear only on U1 (either S1 or S2 
>depending on scheduler).
>
>Ad nausium.
>
>
>Of coures there is nothing stopping you from unifying three bricks, or even 
>unifying an afr to afr.
>
>
>i.e. (might need a mono spaced font to see correctly...)
>
>                         A5
>             +-----------------------+
>             |                       |
>             U1                      U2
>      +-------------+           +---------+
>      |             |           |         |
>      A1            A2          A3        A4
>  +---+---+   +---+---+---+   +---+   +---+---+
>  |   |   |   |   |   |   |   |   |   |   |   |
>S01 S02 S03 S04 S05 S06 S07 S08 S09 S10 S11 S12
>
>
>Where Sxx = Server bricks
>        Ax = AFR brick
>        Ux = Unify brick
>
>
>
>So in this configuration (which you have already worked out i'm sure) that 
>if you save something *:2, then it will appear in both U1 and U2, which 
>means (depending on the spec from a[1-4], assume *:2) it will appear in 
>either A1 or A2 (because of the unify), AND it will also appear in either 
>A3 or A4. etc etc etc.....
>
>I think i've laboured the point far enough :)
>
>
>
>
>>
>>
>>>>4) In my application the server is also the client, in my current config
>>>>when one out of 3 servers is done I can no longer write, even tho I am
>>>>telling my config to write to the local brick. Is there any way to fix
>>>>this? If a note is down I understand how I would not have access to the
>>>>files, but I don't want to take down the full cluster.
>>>
>>>I'm note sure sorry. Maybe one of the devs can clarify that. I know
>>>there was an issue with an earlier relase to do with AFR. When the first
>>>brick was down then afr was no longer available.
>>
>>
>>Ah... That could be it.
>
>Which version of glusterfs are you using? tla, pre ?
>
>(that issue has been fixed for a little while now, so if your using pre6 
>you shoulnd't have come across it)
>
>
>
>
>
>Matt.
>
>
>
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