altering defaults

altering defaults

[prad]

i'm new to xfs (courtesy of most helpful and encouraging commentary by
stan hoeppner!) and i've seen some advice which says to make the 
block size     -> 512
directory size -> 4096

on the other hand, i've also come across webpages which say don't mess
around! keep the defaults as they are unless you are absolutely sure
that changing it suits your purpose and know why.

my question is for the data storage area on a web/email server. we're
mainly going to have small files there and the email part will have only
temporary files for the most part since people will download (ie pop).

it makes sense to make the block size = 512, but i wonder if it really
matters noticeably. the server is not a heavily visited one and only on
very rare occasions will we get around 50000 hits/day - most of the time
we're looking at under 10000 and that is with all the domains combined.

-- 
in friendship,
prad

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Re: altering defaults

[Michael Weissenbacher]

Hi Prad!
> on the other hand, i've also come across webpages which say don't mess
> around! keep the defaults as they are unless you are absolutely sure
> that changing it suits your purpose and know why.
> 
I would do it exactly that way. XFS works reasonably well for all
ordinary things with the defaults (under the assumption that you are
using a reasonably up-to-date version of xfsprogs i.e. mkfs.xfs) and you
shouldn't fiddle with them unless you have very good reasons doing so.
Considering your current load on the server it shouldn't matter at all
and staying with the defaults is also a good way to ensure people will
be able to reproduce problems and help you in case you run into problems.

Just my 2cents

cheers,
Michael

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Re: altering defaults

[Eric Sandeen]

On 6/3/11 10:33 AM, prad wrote:
> i'm new to xfs (courtesy of most helpful and encouraging commentary by
> stan hoeppner!) and i've seen some advice which says to make the 
> block size     -> 512
> directory size -> 4096
> 
> on the other hand, i've also come across webpages which say don't mess
> around! keep the defaults as they are unless you are absolutely sure
> that changing it suits your purpose and know why.

Yup.  See "Q: I want to tune my XFS filesystems for <something> "
http://xfs.org/index.php/XFS_FAQ#Q:_I_want_to_tune_my_XFS_filesystems_for_.3Csomething.3E

> my question is for the data storage area on a web/email server. we're
> mainly going to have small files there and the email part will have only
> temporary files for the most part since people will download (ie pop).
> 
> it makes sense to make the block size = 512, but i wonder if it really
> matters noticeably. the server is not a heavily visited one and only on
> very rare occasions will we get around 50000 hits/day - most of the time
> we're looking at under 10000 and that is with all the domains combined.

If space efficiency is a consideration then smaller blocksizes might
be useful.  Not so much for hits per day, but for how many files you expect
to store at any one time; you'll waste ((blocksize / 2) * nr files) on average.

-Eric

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Re: altering defaults

[prad]

Eric Sandeen <sandeen@sandeen.net> writes:

> If space efficiency is a consideration then smaller blocksizes might
> be useful.  Not so much for hits per day, but for how many files you
> expect to store at any one time; you'll waste ((blocksize / 2) * nr
> files) on average.
>
space is not likely an issue at all.
if there is no efficiency issue the usage of 4096 bytes hardly seems
significant.

so thx eric and michael for your input on this!
we'll leave things alone. :D

-- 
in friendship,
prad

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