[Gluster-devel] glusterfs stripe

Raghavendra G raghavendra.hg at gmail.com
Fri Jul 18 05:07:59 UTC 2008

Hi John,

On Thu, Jul 17, 2008 at 5:09 PM, John Marshall <John.Marshall at ec.gc.ca>

> Raghavendra G wrote:
>> Hi John,
>> Please find the inlined comments.
>> On Thu, Jul 17, 2008 at 2:53 AM, John Marshall <John.Marshall at ec.gc.ca<mailto:
>> John.Marshall at ec.gc.ca>> wrote:
>>    Hi,
>>    I was testing out the glusterfs "type cluster/stripe" and saw in
>>    the output:
>>    -----
>>    2008-07-16 22:48:12 D [fuse-bridge.c:1604:fuse_writev_cbk]
>>    glusterfs-fuse: 169275: WRITE => 131072/131072,21474185188/21474316260
>>    2008-07-16 22:48:12 D [fuse-bridge.c:1641:fuse_write]
>>    glusterfs-fuse: 169276: WRITE (0x80560b0, size=131072,
>>    offset=21474316260)
>>    -----
>>    Whether the client is configured with "option block-size *:4MB" or
>>    "option block-size *:1MB" does not seem to change what appears
>>    above to be write() operations of 128KB at a time. Am I understanding
>>    this correctly?
>> "option block-size " is specific to cluster/stripe xlator. It determines
>> the size of the chunks the file has to be sliced into and distributed among
>> stripe's children. It does not affect the sizes in which fuse does
>> writes/reads.
> Is there any way to change the size of the writes/reads? Have you done any
> tests to see the impact of going to a larger value than 128KB?

Will get back to you about this.

> As a side question, must the block-size remain the same for the life of the
> filesystem? I.e., if the fs was used with block-size of 4MB, then mounted
> later with 1MB, would this mess things up?

If the back-end file-system supports extended attributes, Changing of
block-size should not be a problem, since stripe stores the block-size at
the time of file creation as an extended attribute.  It then uses the stored
attribute value in further reads/writes. Otherwise, the block-size should
remain the same for the life of the file-system.

> Thanks,
> John

Raghavendra G

A centipede was happy quite, until a toad in fun,
Said, "Prey, which leg comes after which?",
This raised his doubts to such a pitch,
He fell flat into the ditch,
Not knowing how to run.

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