[OpenAFS-devel] Re: afscache on UFS+logging or ZFS?

[Robert Milkowski]

On 05/08/2010 09:40, Mattias Pantzare wrote:
>>
>> Actually I believe there is another way which is less expensive. The
>> underlying problem is that once zfs sets a recordsize for a given file it
>> will stick to it forever. So if you create a new file and initially write
>> more than 128KB of data with a default recordsize of 128KB zfs will use a fs
>> blocksize of 128KB, even if file is truncated later on. However if you would
>> create a file and initially write only lets say 1KB it will choose a 1KB
>> recordsize and then stick to it regardless of how much data is being
>> written. But then it is easier for a sysadmin to just limit the recordsize
>> to 8kb (or 1kb, or whatever) I guess. Afsd could check recordsize during
>> startup and issue a warning with recommendation to lower it to a smaller
>> value.
>>      
> No, that is not how it works. A file will stick to the recordsize that
> was set for the filesystem when the file was created, regardless of
> the size of inital writes.
>
> A file smaller than recordsize will have a smaller record but that
> will grow to recordsize when you write more data.
>
>    

Yes, you are actually right. I've just double checked.

-- 
Robert Milkowski
http://milek.blogspot.com