Hi,

We're running Suse Linux Enterprise Server on x86 and with the latest SLES11SP1 release notes comes this announcement:

"The RAW devices are deprecated and will be removed with one of the next Service Packs or SUSE Linux Enterprise Server 12."

I'm about to reinstall Informix onto new drives so might as well migrate to cooked files.

What filesystem is recommended? Are there any significant performance issues nowadays?

Currently I have two raw devices which contain a total of 18 chunks. I would like to see them as 18 files on four different drives/partitions after the migration. I can't find any documentation on migrating to cooked files. Is this even possible?

Using Informix 11.50.UC7.

Regards,

Aleksander Kamenik
System Administrator
Krediidiinfo AS
an Experian Company
Phone: +372 665 9649
Email: aleksander (AT) krediidiinfo (DOT) ee

http://www.krediidiinfo.ee/
http://www.experiangroup.com/

Yeah, Linus has been trying to get rid of RAW files for many years. I wish
he'd just give it up. Anyway, there is no problem using cooked files, and
migrating the data is as simple as dd'ing the data from the RAW devices to
new filesystem files and then relinking the link paths that IDS using to
access the RAW devices to the filesystem files. You should use the simplest
filesystem available, no journalled filesystems like EXT3 and EXT4. I would
suggest just using an old EXT2 filesystem as the best choice. It's very low
overhead compared to the more modern filesystems.

Another option, BTW, would be to use COOKED (aka block) devices rather than
filesystem files. COOKED devices tend to be a little faster than filesystem
files even with DIRECT_IO enabled on both.

Art

Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
IIUG Board of Directors (art (AT) iiug (DOT) org)

Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Advanced DataTools, the IIUG, nor any other
organization with which I am associated either explicitly, implicitly, or by
inference. Neither do those opinions reflect those of other individuals
affiliated with any entity with which I am affiliated nor those of the
entities themselves.



On Wed, Aug 25, 2010 at 10:43 AM, Aleksander Kamenik <
aleksander (AT) krediidiinfo (DOT) ee> wrote:

On 25 August 2010 16:35, Art Kagel <art.kagel (AT) gmail (DOT) com> wrote:
Install free Solaris and continue to use the ease, speed and
versitility of raw space !!!

Keith

This would create 2 files instead of 2 raw devices. Any way to split the raw device into separate files where each file would corresponding to a chunk? I think it might be possible using dd's skip and count options.

How I can I change paths in Informix? root dbs is specified in the onconfig file and that's in one chunk fortunately, but I don't know how to change the paths for all the other chunks. I also don't know what you mean by relinking.

Makes sense, thanks.

What do you mean by that; that each chunk or set of chunks would have their own partition on disk? So instead on /dev/raw/raw1 I'd have /dev/sda1 for example?




Aleksander Kamenik
System Administrator
Krediidiinfo AS
an Experian Company
Phone: +372 665 9649
Email: aleksander (AT) krediidiinfo (DOT) ee

http://www.krediidiinfo.ee/
http://www.experiangroup.com/

See my comments below.

Art

Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
IIUG Board of Directors (art (AT) iiug (DOT) org)

Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Advanced DataTools, the IIUG, nor any other
organization with which I am associated either explicitly, implicitly, or by
inference. Neither do those opinions reflect those of other individuals
affiliated with any entity with which I am affiliated nor those of the
entities themselves.



On Wed, Aug 25, 2010 at 12:17 PM, Aleksander Kamenik <
aleksander (AT) krediidiinfo (DOT) ee> wrote:

Ahh, I didn't understand that you are using two large RAW devices and using
offsets to create several chunks in each device. OK, you have two options:

1. Create one big file for each raw device replacement and continue using
the existing offsets, or
2. Use ontape or onbar to archive your server (which you should be doing
already) then create (ie touch) the new filesystem files one for each chunk,
and restore the server from the archive using ontape/onbar chunk renaming
feature to migrate each chunk into a new filesystem file with a zero offset.

You can't just use dd with skip and count to copy the data from the two
large raw devices into many smaller files because Informix expects that the
data for each chunk is located at a specific offset from the beginning of
the file.


OK, two separate questions. As to links, the path that you give to onspaces
when you create a new chunk (and that you place into the ROOTPATH parameter
in the ONCONFIG file, should NEVER be the actual path to the file or device
but a symbolic link. That allows you to easily move chunks from one device
to another without Informix having to know about it at all. This was VERY
important prior to Informix 10.00 because there was no facility to rename
chunks prior to that release. Currently you can rename chunk paths using
ontape or onbar, but ONLY during a restore of the server from an archive.
Since this is usually a lengthy process it remains more convenient to use
symbolic links whenever possible. So, what I'm saying is that in the new
storage, you will have chunks in say three filesystems. Let's call them
/informix/disks_1, /informix/disks_2, and /informix/disks_3. I'm
recommending that instead of using those paths when you pass the chunk paths
to ontape/onbar to remap them from the RAW devices, create another
directory, say /informix/all_disks. While in /informix/disks_1 you will
have chunk files named something like dbspace_1_chunk_1, and
dbspace_1_chunk2 and in /informix/disks_2 you will have chunk files named
something like dbspace_2_chunk_1, etc. You will then create links in
/informix/all_disks for all of those chunks and use the link's paths instead
of the actual file paths. That way if someday you add a new set of disks
and decide to spread the load around to the new filesystem it will just be a
matter of shutting down the engine, copying the file(s) to the new
filesystem, and changing the appropriate links in /informix/all_disks to
point to the new file locations and restarting the engine. no muss, no
fuss, no restore needed.

For new, because you will have to change offsets from non-zero ones to
zeros, and from two paths for all chunks to many different paths, you will
have no option really other than to do a restore or to live with just two
huge files.


Yes, exactly. On other UNIX-like OSes (than Linux) all RAW devices have a
directly corresponding COOKED device through the single disk device driver,
so you would just have to relink your chunk paths from the RAW device to
point to the COOKED device and restart the engine. POOF! In Linux, since
the RAW devices are not handled by the same OS driver as COOKED devices, and
the physical data layout is not identical (RAW devices have some hidden
overhead at the beginning of the device's storage that's not part of the
device's data area), you can't get away that easy. You would have to copy
the data from the RAW device to a COOKED device. If you will need to create
the COOKED devices on the same storage you are using for the RAW data now,
that would probably mean either having some intermediate storage (copy from
RAW to intermediate, destroy RAW, create COOKED, copy data to COOKED) or
going through the ontape/onbar restore process after destroying the RAW
devices and recreating them as COOKED devices.

On Wed, Aug 25, 2010 at 3:43 PM, Aleksander Kamenik <
aleksander (AT) krediidiinfo (DOT) ee> wrote:


Yes, it's possible. You should use a non journalled filesystem (search for
recent discussions on this in the mailing list).
You should also activate DIRECT_IO in your instance configuration.

Regarding the "migration" itself there isn't really too much to do.... It
really depends on what you're about to do... Let see.
You talk about "installing Informix on two new drives". What exactly does it
mean? Are you talking about just the product installation or the data
chunks?
How were you plan to move the data if you were going to use RAW devices? An
Informix backup/restore or an offline "dd" or anything else?

The idea is that you need to create the new files (after the filesystem
creation a simple "touch/chmod" will do....
Then you need to copy the data in a consistent way....
And finally you need to tell your instance that it should be using the new
files and not the old ones...
If you're using symbolic links for your current RAW devices, you just have
to point them to the new files...

Regarding ways to copy data.... several options:

1- OFFLINE with dd OS command
2- OFFLINE with backup/restore (using the rename option to move the chunks,
or simply changing the links)
3- ONLINE with something that can synchronize the files "online".... This
can be tricky or challenging.... I've used it with logical volume managers
(between two raw devices, followed by a short engine stop to change the
links). You could also use Informix mirror ability.... I'd have to check the
"after synchronize steps"....

Tell us more about your plan of activities (forgetting the move from RAW to
filesystem) and then we can give you more help

Regards.

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

On Wed, Aug 25, 2010 at 10:00 PM, Fernando Nunes <domusonline (AT) gmail (DOT) com>wrote:


Well.... I'm now feeling officially stupid... Somehow I missed all the
discussion going on... I think all that I wrote was already detailed...
Sorry...

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

Keith Simmons wrote:
Do you mean OpenSolaris? If so take a look at what's been happening in
the last week or so, e.g.
http://www.theinquirer.net/inquirer/...-board-resigns

It seems that OS could be a dead end until Illumos (
http://www.illumos.org ) is ready to provide a way forward.

--
Ian

The Hotmail address is my spam-bin. Real mail address is iang
at austonley org uk

"Aleksander Kamenik" <aleksander (AT) krediidiinfo (DOT) ee> wrote

Hi,

"The RAW devices are deprecated and will be removed with one of the next
Service Packs or SUSE Linux Enterprise Server 12."

I'm about to reinstall Informix onto new drives so might as well migrate to
cooked files.

What filesystem is recommended? Are there any significant performance issues
nowadays?

Avoid a journaled FS. So, ext2 is a good choice.
Migration is easy enough
1. If you have used symbolic links for your chunk names, just take a level
0, change your links to the new file system files, and do a restore
2. If you have NOT used links, firstly you should be executed. If you
survive this, use an ontape "redirected restore" (RTFM) and use links this
time!

regards

Thanks Art and everybody who helped out with this.

I'll use the ontape restore with chunk renaming method. ext2 will be used on the data partitions. I'll enable DIRECT_IO. I'll use symlinks.

Long explanation:

I should have explained better; I have two devices one of which contains most of the chunks using offsets (the second has only the logical log chunk), so ontape with chunk rename is the only way to go for me. I'll be using 4 different drives (RAID1) where the chunks will go.

No, symlinks are not used, but I didn't install this instance either. And yes I'll definitely use them now.

Thanks again,

Aleksander Kamenik
System Administrator
Krediidiinfo AS
an Experian Company
Phone: +372 665 9649
Email: aleksander (AT) krediidiinfo (DOT) ee

http://www.krediidiinfo.ee/
http://www.experiangroup.com/