Resizing /var (maybe off topic)

Wojciech Puchar wojtek at tensor.3miasto.net
Sun Jun 12 12:41:28 GMT 2005


i'm using different unices for 7 years and excluding few cases i never 
made other partitioning scheme than 2 partitions: swap and /

i have no problems like "there's out of space in partition x while plenty 
of y".
it's far easier to do backups too (single dump).

i read lots of howtos about this both in FreeBSD, NetBSD and (few years 
ago) in linux.

all states that multiple partition gives you:

1) better performance
2) better recovery in case of crash


in case of 2-nd argument - for me it's complete nonsense. in case of disk 
crash it doesn't make any difference, in case of filesystem crash no 
difference anyway.

UFS/FFS filesystem is anyway "partitioned" with "cylinder groups" and 
no destruction makes whole filesystem unreadable. statistically - with 
similar amount of destruction (writing nonsense because of hardware or 
software failure) same amount of data is unaccessible on given space, no 
matter if it's one or 20 filesystems.

it was indeed true for old BSD unix in PDP11 times that used "old 
filesystem" with all inodes on the beginning of partition. in case of bad 
write at the beginning of disk all content of one partition were lost. and 
i thing it's a myth copied years and years till today.


in case of 1-st argument - in theory it's true. in theory too - difference 
will be minimal unless you have your partitions very close to full and 
fragmentation starts to make big change on performance. but - that case - 
you would like to have one partition too to avoid problem with space!!

in linux (at least 2.0 and 2.2 kernels) it's worse because linux tends to 
optimize disk access on filesystem layer much better than on device driver 
layer. found experimentally that copying files on same partition is much 
faster than crossing different partition. in second case lot of 
disk head moves are done. but this is linux case...

in both FreeBSD and NetBSD it looks in my test that the difference is 
really difficult to measure.


fsck speed is same in checking one partition or many smaller. and it 
doesn't matter at all as FreeBSD (and NetBSD) doesn't crash every few 
hours like windows

On Sun, 12 Jun 2005, Wojciech Puchar wrote:

> Date: Sun, 12 Jun 2005 14:12:41 +0200 (CEST)
> From: Wojciech Puchar <wojtek at tensor.3miasto.net>
> To: ptitoliv <ptitoliv at frenchsuballiance.cjb.net>
> Cc: freebsd-questions at freebsd.org
> Subject: Re: Resizing /var
> 
>> But there are some constraints :
>> 
>> - I have no free unpartitioned space available
>> - I can't format any partition because and I can't loose datas
>> 
>> Is there any solution with some BSD tools in order to solve this problem ?
>
> link /var/spool to /usr/spool :)
>
>> 
>> Thank you for your answers
>> 
>> Best Regards,
>> Ptitoliv
>> 
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