re: the chunk move from raw to FS, I have just completed something similar with 18 systems, each comprised of primary, HDR and 2RSS nodes.
The only two issues that were found,
1 a need a minor outage to allow mirroring
2 a minor outage after it was complete.
The second was more irritating, without it the backups wouldn't restore - note I never did serious diagnostics as this was all an emergency change to get off ext4-nologging due to the RH 'not-a-bug' kernel issue
Cheers
Paul
On 3/7/2023 8:15 AM, Jared Heath via IBM Community wrote:
01000186bc6d129b-8ad58b5e-3b30-438a-9a93-1c1258253d50-000000@email.amazonses.com"> Art, thanks for the options. This is a 14.10 system and I was unaware of the new mirroring functionality.....I will look into that. Can that...
Original Message:
Sent: 3/7/2023 9:15:00 AM
From: Jared Heath
Subject: RE: Raw Devices are Deprecated in SLES 15 SP4. I need help figuring out what to do.
Art, thanks for the options. This is a 14.10 system and I was unaware of the new mirroring functionality.....I will look into that. Can that function to remove the fragmentation or is the mirroring at the chunk level?
I thought that ER required everything to be identical at the chunk level also....is that something newer for ER?
Option 2 is my worst case scenario, but is a seamless simultaneous fix for both items (albeit a major piece of work)
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Jared Heath
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Original Message:
Sent: Fri March 03, 2023 06:14 AM
From: Art Kagel
Subject: Raw Devices are Deprecated in SLES 15 SP4. I need help figuring out what to do.
Jared:
First, as Andreas points out, your buffer cache should be mitigating 98-99% of any IO performance issues, so that 5% is more like 0.05% of your total IO time. Next, how to migrate to new storage. If you are running v14.10, you can use the new mirror swap feature. Simply mirror each raw chunk with a filesystem file. Once the mirrors have completed syncing swap each primary chunk with its mirror so that the new chunks are the primaries then you can drop the mirror/old raw chunks.
Reorganizing your dbspaces into fewer chunks is more difficult. There are three ways you could do it:
- Create new dbspaces in cooked files then ALTER FRAGMENT every table into the new dbspaces. That does you can drop the now empty dbspace. Problem: you cannot move the catalog tables for your databases, so those dbspaces cannot be dropped, though some of the chunks that have emptied out could be dropped from these dbspaces.
- Unload all user databases (don't forget changes you have made in system databases like installing my ratios functions in sysmaster. Then you can trash the entire instance and rebuild it from scratch in the new storage and reload everything. So dbexport/myexport then dbimport/myimport. Not fun, but ...
- Create a new instance in the new storage, recreate your databases there empty or copied using export/import, then use ER to sync the new server from the original. Finally shutdown both servers, rename the new one and bring it up as the only server instance.
Art
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Art S. Kagel, President and Principal Consultant
ASK Database Management Corp.
www.askdbmgt.comOriginal Message:
Sent: Fri March 03, 2023 12:34 AM
From: Jared Heath
Subject: Raw Devices are Deprecated in SLES 15 SP4. I need help figuring out what to do.
Unfortunately 5% performance loss is going to be a big deal. They already think it should run 30-40% faster than it does, but that is entirely out of my hands mostly.
My biggest issue right now is how do I even go about setting this up on ext2. Just chunks that are formatted? How do I move the data out of the raw spaces onto the cooked files? dd or is there something better? Should I approach this one dbspace at a time? We really (really) need to resize some of these spaces due to some significant fragmentation over the years....is there an easy way to merge table spaces with multiple chunks into one space while doing this? Is it worth it?
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Jared Heath
Original Message:
Sent: Thu March 02, 2023 03:41 PM
From: Paul Watson
Subject: Raw Devices are Deprecated in SLES 15 SP4. I need help figuring out what to do.
Check out DIRECTIO and do some performance tests, and see what you see. Not as bad as you think (~5% and ext2)
Cheers
Paul
On 3/2/2023 2:28 PM, Jared Heath via IBM Community wrote:
01000186a402bf92-9f3b9eb2-589d-406b-8418-4e4d04a25849-000000@email.amazonses.com"> Surprise! Suse Enterprise 15 SP4 deprecates raw device support. As in, you can't do the modprobe to enable the devices and the actual raw...
| Raw Devices are Deprecated in SLES 15 SP4. I need help figuring out what to do. | | | | | | Surprise! Suse Enterprise 15 SP4 deprecates raw device support. As in, you can't do the modprobe to enable the devices and the actual raw related OS level objects are no longer there. This probably isn't a surprise to some of you, but I really don't have any idea where to go and what to do. Raw devices vs cooked were a solid 8-10% performance increase when I first migrated our database from HP-UX to Linux 10 years ago. I can't imagine it isn't a non-negligible hit today on same hardware, but it seems I have two options, never upgrade (not really an option), find another OS that supports raw devices AND Informix (probably not a solution) or cut over to cooked files and have the business lose their minds over it. With that said, I don't have any idea how to even start migrating the chunks, what types of filesystems to use, how to set the engine up etc. I'm hoping there is some resource out there somewhere I haven't stumbled on yet to goes into (great, significant) detail on doing this.....I haven't found one yet. Has anybody done this? ------------------------------ Jared Heath ------------------------------ | | | Reply to Group Online View Thread Recommend Forward Flag as Inappropriate | | |
-- Paul Watson Oninit www.oninit.com Tel: +1 913 364 0360 Cell: +1 913 387 7529 Oninit® is a registered trademark of Oninit LLC If you want to improve, be content to be thought foolish and stupid Failure is not as frightening as regret
Original Message:
Sent: 3/2/2023 3:28:00 PM
From: Jared Heath
Subject: Raw Devices are Deprecated in SLES 15 SP4. I need help figuring out what to do.
Surprise! Suse Enterprise 15 SP4 deprecates raw device support. As in, you can't do the modprobe to enable the devices and the actual raw related OS level objects are no longer there.
This probably isn't a surprise to some of you, but I really don't have any idea where to go and what to do. Raw devices vs cooked were a solid 8-10% performance increase when I first migrated our database from HP-UX to Linux 10 years ago. I can't imagine it isn't a non-negligible hit today on same hardware, but it seems I have two options, never upgrade (not really an option), find another OS that supports raw devices AND Informix (probably not a solution) or cut over to cooked files and have the business lose their minds over it.
With that said, I don't have any idea how to even start migrating the chunks, what types of filesystems to use, how to set the engine up etc. I'm hoping there is some resource out there somewhere I haven't stumbled on yet to goes into (great, significant) detail on doing this.....I haven't found one yet.
Has anybody done this?
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Jared Heath
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