Craig James wrote:
> Dave Cramer wrote:
>>
>> On 16-Mar-08, at 2:19 AM, Justin wrote:
>>
>>>
>>> I decided to reformat the raid 10 into ext2 to see if there was any
>>> real big difference in performance as some people have noted here
>>> is the test results
>>>
>>> please note the WAL files are still on the raid 0 set which is still
>>> in ext3 file system format. these test where run with the fsync as
>>> before. I made sure every thing was the same as with the first test.
>>>
>> This is opposite to the way I run things. I use ext2 on the WAL and
>> ext3 on the data. I'd also suggest RAID 10 on the WAL it is mostly write.
>
> Just out of curiosity: Last time I did research, the word seemed to be
> that xfs was better than ext2 or ext3. Is that not true? Why use
> ext2/3 at all if xfs is faster for Postgres?
>
> Criag

And let's see if I can write my own name ...

Craig

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On 16-Mar-08, at 3:04 PM, Craig James wrote:

> Dave Cramer wrote:
>> On 16-Mar-08, at 2:19 AM, Justin wrote:
>>>
>>> I decided to reformat the raid 10 into ext2 to see if there was
>>> any real big difference in performance as some people have noted
>>> here is the test results
>>>
>>> please note the WAL files are still on the raid 0 set which is
>>> still in ext3 file system format. these test where run with the
>>> fsync as before. I made sure every thing was the same as with
>>> the first test.
>>>
>> This is opposite to the way I run things. I use ext2 on the WAL and
>> ext3 on the data. I'd also suggest RAID 10 on the WAL it is mostly
>> write.
>
> Just out of curiosity: Last time I did research, the word seemed to
> be that xfs was better than ext2 or ext3. Is that not true? Why
> use ext2/3 at all if xfs is faster for Postgres?
>
I would like to see the evidence of this. I doubt that it would be
faster than ext2. There is no journaling on ext2.

Dave

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On Sun, Mar 16, 2008 at 1:36 PM, Dave Cramer <pg@fastcrypt.com> wrote:
>
> On 16-Mar-08, at 3:04 PM, Craig James wrote:
> > Just out of curiosity: Last time I did research, the word seemed to
> > be that xfs was better than ext2 or ext3. Is that not true? Why
> > use ext2/3 at all if xfs is faster for Postgres?
> >
> I would like to see the evidence of this. I doubt that it would be
> faster than ext2. There is no journaling on ext2.

Well, if you're dropping a large table ext2/3 has that very long wait
thing that can happen. Don't know how much battery backed cache would
help.

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OK i'm showing my ignorance of linux. On Ubuntu i can't seem to figure
out if XFS file system is installed, if not installed getting it
installed.

I would like to see the difference between XFS and ext2 performance
numbers.

any pointers would be nice. I 'm not going to reinstall the OS. Nor do
i want to install some unstable library into the kernel.

Dave Cramer wrote:
>
> On 16-Mar-08, at 3:04 PM, Craig James wrote:
>
>> Dave Cramer wrote:
>>> On 16-Mar-08, at 2:19 AM, Justin wrote:
>>>>
>>>> I decided to reformat the raid 10 into ext2 to see if there was any
>>>> real big difference in performance as some people have noted here
>>>> is the test results
>>>>
>>>> please note the WAL files are still on the raid 0 set which is
>>>> still in ext3 file system format. these test where run with the
>>>> fsync as before. I made sure every thing was the same as with the
>>>> first test.
>>>>
>>> This is opposite to the way I run things. I use ext2 on the WAL and
>>> ext3 on the data. I'd also suggest RAID 10 on the WAL it is mostly
>>> write.
>>
>> Just out of curiosity: Last time I did research, the word seemed to
>> be that xfs was better than ext2 or ext3. Is that not true? Why use
>> ext2/3 at all if xfs is faster for Postgres?
>>
> I would like to see the evidence of this. I doubt that it would be
> faster than ext2. There is no journaling on ext2.
>
> Dave
>

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Well every thing worked right up to the point where i tried to mount the
file system

Warning: xfs_db: /dev/sdb1 contains a mounted file system

fatal error -- couldn't initialize XFS library.

think i'm missing something???

Craig Ringer wrote:
> Justin wrote:
>
>> OK i'm showing my ignorance of linux. On Ubuntu i can't seem to figure
>> out if XFS file system is installed, if not installed getting it
>> installed.
>>
>
> There are two parts to the file system, really. One is the kernel driver
> for the file system. This is almost certainly available, as it will ship
> with the kernel. It might be a module that is loaded on demand or it
> might be compiled into the kernel its self.
>
> On my Debian Etch system it's a module, xfs.ko, that can be loaded
> manually with:
>
> modprobe xfs
>
> ... however, you should not need to do that, as it'll be autoloaded when
> you try to mount an xfs volume.
>
> The other part to the file system is the userspace tools for creating,
> checking, resizing, etc the file system. An `apt-cache search xfs' shows
> that these tools have the package name xfsprogs, at least on Debian.
>
> You can install them with "apt-get install xfsprogs". If they're already
> installed no action will be taken.
>
> When xfsprogs is installed you can use mkfs.xfs (see: man mkfs.xfs) to
> format a block device (say, a partition like /dev/sda1 or an LVM logical
> volume like /dev/SOMELVMVG/somelvmlv) with the xfs file system.
>
> Once the file system is formatted you can mount it manually with the
> mount command, eg:
>
> mkdir /mnt/tmp
> mount -t xfs /dev/sda1 /mnt/tmp
>
> ... or have it mounted on boot using an fstab entry like:
>
> /dev/sda1 /path/to/desired/mountpoint xfs defaults 0 0
>
> --
> Craig Ringer
>
>