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Old 05-19-2010, 07:53 PM   #1
Erik_FL
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Slackware Fake Hardware RAID - Suggestions


Here are my suggestions.

Slackware should maintain a "dmraid" package at least with the existing functionality of "dmraid". That should include support for 64-bit. If possible, "dmraid" should be supported in "initrd".

Slackware should encourage the addition of more metadata formats to "mdadm" and update the initrd to work with "mdadm" and fake raid metadata formats.

Comments:

I've been using Slackware since version 10 and it has progressively gotten better at supporting fake hardware RAID. Improvements in the "initrd" scripts and startup scripts have eliminated the need for editing to support RAID. To use "dmraid" I only have to make a small change to the "init" script for the initrd. There are a few other issues that can be solved using "udev" rules and by creating some device special files to use before "udev" starts.

However, that has always required extra software. My problem has been that software such as "dmraid" lags behind changes in the Linux kernel and distros unless it is a standard part of the distros. Although "mdadm" has recently added support for one fake hardware RAID format (Intel Matrix Storage Manager), that version has not yet been added to Slackware and the scripts for creating and running the initrd.

It's not clear to me if "dmraid" is (still) a package included with Slackware, but I hope that it will be in the future. So far it is the only thing that I have been able to use reliably for fake hardware RAID on Slackware. Unfortunately I can't tell if "dmraid" is still being maintained, or if it's just a legacy package still in some distros. My current problem is that I can't find or create a working 64-bit version of "dmraid" for Slackware. To be more accurate, I think it is some of the libraries used by "dmraid" that are missing for a 64-bit OS.

I have been able to get the newest version of "mdadm" to detect my Intel RAID arrays but that version is not yet a part of Slackware. Also, I have not been able to get an initrd to work with "mdadm". Even if "mdadm" is updated in Slackware it only supports one fake hardware RAID format. I still think there is a need for "dmraid" on 64-bit Slackware.

There are really two issues keeping me from using Slackware 64-bit.

The first one is my fake hardware RAID (Intel Matrix Storage Manager) and the second is my ATI graphics card. Getting the 32-bit driver working was painful and I haven't figured out how to do that with the 64-bit driver.
 
Old 05-19-2010, 08:14 PM   #2
mRgOBLIN
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Hi Erik_FL,

We did look at including the latest (3.1.2) version of mdadm. After looking into the changes required for a proper implementation it was a little too risky this close to release time.

It will be something we will look into further early in the next -current cycle though and it will almost certainly be mdadm rather than dmraid. (assuming we can get it functioning correctly).
 
Old 05-20-2010, 12:04 AM   #3
Erik_FL
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Quote:
Originally Posted by mRgOBLIN View Post
Hi Erik_FL,

We did look at including the latest (3.1.2) version of mdadm. After looking into the changes required for a proper implementation it was a little too risky this close to release time.

It will be something we will look into further early in the next -current cycle though and it will almost certainly be mdadm rather than dmraid. (assuming we can get it functioning correctly).
That's great. Hopefully more metadata formats will be supported by mdadm in the future. Thanks to all of you who make Slackware a reliable and useful Linux distribution.

I like the idea of using a program to interpret the metadata and configure a standard RAID driver. Most fake hardware RAID on Windows uses proprietary drivers and those are not always maintained well. Perhaps "mdadm" will eventually support some kind of script or plug-in file format to define new metadata formats without modifying the program.
 
Old 05-20-2010, 03:26 AM   #4
LuckyCyborg
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Smile

Quote:
Originally Posted by mRgOBLIN View Post
Hi Erik_FL,

We did look at including the latest (3.1.2) version of mdadm. After looking into the changes required for a proper implementation it was a little too risky this close to release time.

It will be something we will look into further early in the next -current cycle though and it will almost certainly be mdadm rather than dmraid. (assuming we can get it functioning correctly).
I am a happy user's mdadm-3.1.2.

My configuration is a partitionable RAID0 (yep, no LVM required) with a RAID1 for /boot, and a RAID5 for data.

The big advantage is that the 3.X versions interact with udev excellent, and it correctly finds my software RAID partitions in the initrd, without other changes.

So mdadm-3.1.2 allows me to have a partitioned RAID device, so as to avoid the use of extra LVM layer.

The only notable difference from the version 2.6.x is that it creates default RAID arrays with metadata version 1.2, which is not bootable by LILO / GRUB.

Therefore, you must specify an additional parameter: --metadata=0.90, if you want to create a "bootable" RAID1 array. However, he gives a warning/question to you and instruct you properly.

So, I don't see why Slackware can't use this superior MDADM versions.
 
Old 05-20-2010, 03:40 AM   #5
mRgOBLIN
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It's not that we can't... in fact I've had a machine running with 3.1.2 and various RAID configurations. It's just that we ran out of time to properly test this.

It's a bit too important to just throw in without proper testing and when we do it we want to do it right.

Looks like we'll have some volunteers when it comes to testing time though =)

Last edited by mRgOBLIN; 05-20-2010 at 03:46 AM.
 
Old 05-20-2010, 06:15 AM   #6
LuckyCyborg
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Talking

Quote:
Originally Posted by mRgOBLIN View Post
It's not that we can't... in fact I've had a machine running with 3.1.2 and various RAID configurations. It's just that we ran out of time to properly test this.

It's a bit too important to just throw in without proper testing and when we do it we want to do it right.
MDADM-3.1.2 run flawless in my system and I use the same version in few production servers. Here isn't backward compatibility issues or other things. Only new useful facilities.

I know what scare you: that MDADM-3.X interact with UDEV.

Well, in fact the MDADM-3.X instruct the UDEV only to create some useful device symlinks (to /dev/disk/by-id, /dev/disk/by-uuid and /dev/disk/by-label).

Quote:
Originally Posted by mRgOBLIN View Post
Looks like we'll have some volunteers when it comes to testing time though =)
Well, as long as you do not destroy my RAID5 array, where I keep data, I'm happy to register as a beta tester.

Last edited by LuckyCyborg; 05-20-2010 at 06:16 AM.
 
  


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