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Old 08-14-2008, 12:33 PM
"Mag Gam"
 
Default small blocks

I am trying to understand what the purpose of having small blocks per
inode. I know you can cram more inodes per filesystem, but what is the
downside?

TIA

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Old 08-14-2008, 01:49 PM
Eric Sandeen
 
Default small blocks

Mag Gam wrote:
> I am trying to understand what the purpose of having small blocks per
> inode. I know you can cram more inodes per filesystem,

the main result is that you waste less space per file, since for
randomly-sized files you waste half a block(size) per file.

> but what is the
> downside?

More overhead for management, and more importantly, I still think there
is a bug lurking somewhere with block size < page size (rpm tends to hit
it for some people).

-Eric

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Old 08-15-2008, 11:21 AM
"Mag Gam"
 
Default small blocks

Hmm, I am wasting less space when I lower the ratio from 4096 to 1024
(the minimum). Why don't more people do this, since its frugal.
I guess your point of more overhead, but what causes more overhead?
Also, do you have the buzilla number I can investigate for this?

Sorry for such a newbie question.
TIA

On Thu, Aug 14, 2008 at 9:49 AM, Eric Sandeen <sandeen@redhat.com> wrote:
> Mag Gam wrote:
>> I am trying to understand what the purpose of having small blocks per
>> inode. I know you can cram more inodes per filesystem,
>
> the main result is that you waste less space per file, since for
> randomly-sized files you waste half a block(size) per file.
>
>> but what is the
>> downside?
>
> More overhead for management, and more importantly, I still think there
> is a bug lurking somewhere with block size < page size (rpm tends to hit
> it for some people).
>
> -Eric
>

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Old 08-15-2008, 01:53 PM
Eric Sandeen
 
Default small blocks

Mag Gam wrote:
> Hmm, I am wasting less space when I lower the ratio from 4096 to 1024
> (the minimum). Why don't more people do this, since its frugal.
> I guess your point of more overhead, but what causes more overhead?
> Also, do you have the buzilla number I can investigate for this?
>
> Sorry for such a newbie question.

Now that I reread, perhaps I gave you the wrong answer anyway.

Are you talking about the -i or the -b option?

-Eric

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Old 08-15-2008, 11:07 PM
"Mag Gam"
 
Default small blocks

Asking about the -i options.

-i bytes-per-inode

The man page states, "This value generally shouldn't be smaller than
the blocksize of the filesystem, since then too many inodes will be
made."

So, whats the problem of having too many inodes


On Fri, Aug 15, 2008 at 9:53 AM, Eric Sandeen <sandeen@redhat.com> wrote:
> Mag Gam wrote:
>> Hmm, I am wasting less space when I lower the ratio from 4096 to 1024
>> (the minimum). Why don't more people do this, since its frugal.
>> I guess your point of more overhead, but what causes more overhead?
>> Also, do you have the buzilla number I can investigate for this?
>>
>> Sorry for such a newbie question.
>
> Now that I reread, perhaps I gave you the wrong answer anyway.
>
> Are you talking about the -i or the -b option?
>
> -Eric
>

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Ext3-users@redhat.com
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Old 08-15-2008, 11:11 PM
Eric Sandeen
 
Default small blocks

Mag Gam wrote:
> Asking about the -i options.
>
> -i bytes-per-inode
>
> The man page states, "This value generally shouldn't be smaller than
> the blocksize of the filesystem, since then too many inodes will be
> made."
>
> So, whats the problem of having too many inodes

You waste space on unused inodes.

And the problem of not having _enough_ is, you can't make new files even
when you have lots of blocks free, and you can't change that after the
fact. It's one of the drawbacks of not dynamically allocating inodes.

-Eric

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