Re: What`s wrong with JFS configuration?

Adding -performance back in so others can learn.

On Apr 26, 2007, at 9:40 AM, Paweł Gruszczyński wrote:

> Jim Nasby napisał(a):
>> On Apr 25, 2007, at 8:51 AM, Paweł Gruszczyński wrote:
>>> where u6 stores Fedora Core 6 operating system, and u0 stores 3
>>> partitions with ext2, ext3 and jfs filesystem.
>>
>> Keep in mind that drives have a faster data transfer rate at the
>> outer-edge than they do at the inner edge, so if you've got all 3
>> filesystems sitting on that array at the same time it's not a fair
>> test. I heard numbers on the impact of this a *long* time ago and
>> I think it was in the 10% range, but I could be remembering wrong.
>>
>> You'll need to drop each filesystem and create the next one go get
>> a fair comparison.
>
> I thought about it by my situation is not so clear, becouse my hard
> drive for postgresql data is rather "logical" becouse of RAID array
> i mode 1+0. My RAID Array is divided like this:
>
>   Device Boot      Start         End      Blocks   Id  System
> /dev/sda1               1      159850   163686384   83  Linux
> /dev/sda2          159851      319431   163410944   83  Linux
> /dev/sda3          319432      478742   163134464   83  Linux
>
> and partitions are:
>
> /dev/sda1     ext2   161117780   5781744 147151720   4% /fs/ext2
> /dev/sda2     ext3   160846452   2147848 150528060   2% /fs/ext3
> /dev/sda3      jfs   163096512   3913252 159183260   3% /fs/jfs
>
> so if RAID 1+0 do not change enything, JFS file system is at third
> partition wich is at the end of hard drive.

Yes, which means that JFS is going to be at a disadvantage to ext3,
which will be at a disadvantage to ext2. You should really re-perform
the tests with each filesystem in the same location.

> What about HDD with two magnetic disk`s? Then the speed depending
> of partition phisical location is more difficult to calculate ;)
> Propably first is slow, secund is fast in firs halt and slow in
> secund halt, third is the fastes one. In both cases my JFS partitin
> should be ath the end on magnetic disk. Am I wrong?

I'm not a HDD expert, but as far as I know the number of platters
doesn't change anything. When you have multiple platters, the drive
essentially splits bytes across all the platters; it doesn't start
writing one platter, then switch to another platter.
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)