Re: [Gluster-devel] Choice of Translator question

[Gareth Bult]

Hi,

I think we're mis-reading the conversation a little.

I agree, with your explanation, it's the same as my explanation and the same as 
a the user guide.
There is no confusion here - it works for me as you describe.

The issue is is that with 3 stripes, the size of each stripe is (n)/3.
For a 90GB file, this is still 30GB per stripe.
Given restarting glusterfsd breaks the "mirrors", this will still require at 
least 30GB to be copied on self-heal.
(which isn't workable)

The way in which this "would" be usable if if the striping process broke the 
file down into "many" files, typically down to the chunk size .. which would 
make the self-heal process reasonably quick. Unfortunately creating a config 
file with 5,000 stripes also seems a little unworkable.

Regards,
Gareth


----- Original Message -----
From: "Csibra Gergo" <address@hidden>
To: address@hidden
Sent: Friday, December 28, 2007 10:21:17 AM (GMT) Europe/London
Subject: Re: [Gluster-devel] Choice of Translator question

Friday, December 28, 2007, 1:05:09 AM, Kevan Benson wrote:

> Gareth Bult wrote:
>> This could be the problem.
>> 
>> When I do this on a 1G file, I have 1 file in each stripe partition of size 
>> ~ 1G.
>> 
>> I don't get (n) files where n=1G/chunk size ... (!)
>> 
>> If I did, I could see how it would work .. but I don't ..
>> 
>> Are you saying I "definitely should" see files broken down into multiple sub 
>> files, or were you assuming this is how it worked?

> That sounds like the striping isn't working

Well, the answer is yes for Gareth and no for Kevan. The stripe
translator works :)

See this:

gergolaptop:/mnt/gluster1# ls -la
összesen 26021
drwxr-xr-x  3 root root      1024 2007-12-28 11:03 .
drwxr-xr-x 17 root root      4096 2007-12-28 10:58 ..
-rw-r--r--  1 root root 104660992 2007-12-28 11:03 glusterimg1
drwx------  2 root root     12288 2007-12-03 22:09 lost+found

As you see the glusterimg1 file looks like 1 100MB size, but...

gergolaptop:/mnt/gluster1# du -h glusterimg1
26M     glusterimg1

It occupies only 26MB (striped to four pieces)

gergolaptop:/mnt/gluster1# df .
Fájlrendszer          1K-blokk   Foglalt    Szabad Fo.% Csatl. pont
/mnt/glusterimg1         99150     31668     62362  34% /mnt/gluster1

And you see here too, the disk is only 100MB size, and only 31668 are
occupied (Foglalt means occupied in hungarian, Szabad is free).

All of the striped files are sparse files. Sparse files are occupy
disk space only they use. So if you create a file, seeks to 100MB, and
write there only 1 byte, the file will looks like a 100MB file, but
will only occupy 1 byte (not 1 byte, 1024,2048,4096 it depends the
block and chunk size of the filesystem).

see more here:

http://en.wikipedia.org/wiki/Sparse_file

-- 
Best regards,
 Csibra Gergo                            mailto:address@hidden



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