Harry M. Aasterud | 1 Jun 2005 15:08

mdamin on Fedora Core 3 - recovery procedures

Hi,

I found this email adress on the website of Neil Brown at
http://cgi.cse.unsw.edu/~neilb/Contact. I hope this email will find its
way to the right person, within reasonable time.

I installed FC3 with server installation. I'm using to identical disks
40 Gb each, no RAID controller. Disc 1 on IDE controler 1, 2 on 2.
During partitioning, I did this:

- deleted all partitions
- created new partition on hda, file system type software RAID, 100 Mb.
This will be boot partition on hda. Did the same on hdc
- created new partition on hda, file system type software RAID, 512 Mb.
This will be swap partition on hda. Did the same on hdc
- created new partition on hda, file system type software RAID, fill to
max size . This will be / partition on hda. Did the same on hdc

Created RAID devices

selected hda1 and hdc1 -> md1
selected hda2 and hdc2 -> md2
selected hda3 and hdc3 -> md3

copied MBR via grub

When doing so, al works fine. Shutting down the system, disconnecting
disc 2, and reboot. Doing cat /proc/mdstat shows only hda1/2/3, which is
correct. just one minor problem: Smartd failed to load during reboot,
though the smard.conf points to both hda and hdc. But the system is
(Continue reading)

Francisco Zafra | 1 Jun 2005 19:51
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RE: Troubles making a raid5 system work.


Thanks Molle,

Finally I made the raid system work fine :-) I followed your steps, I it
worked... That exactly what I did:
- I applied the patch
md-make-raid5-and-raid6-robust-against-failure-during-recovery.patch to my
kernel.
- dd the all the hardisk erasing superblock info and all...
- Create again the array from 0.

I checked the logs and all seems to be right.

Thanks again.

By the way... I have two questions.
1.- This patch will be included in new kernels versions or I have to applied
each time I compile a new kernel version?
2.- Working with big files (700megs) in the RAID comsumes a lot of cpu
resources, is this normal? I have an Pentium 4, 3Ghz and 1GB RAM...

That's all.

> Francisco Zafra wrote:
> >  I have 8 200GB new SATA HDs, mdadm v1.9.0 and kernel 2.6.11.8.
> 
> > When the create command finish proc/mdstats report the following:
> >         md0 : active raid5 sda1[0] sdh1[8] sdg1[6] sdf1[5] sde1[4] 
> > sdd1[3]
> > sdc1[9](F) sdb1[1]
(Continue reading)

Molle Bestefich | 2 Jun 2005 02:56
Picon

Re: Troubles making a raid5 system work.

Francisco Zafra wrote:
> Finally I made the raid system work fine :-)
Cool beans ;-).

> 1.- This patch will be included in new kernels versions or I have to applied
> each time I compile a new kernel version?

It will be included at some point, probably "soon".
I'm not part of that process so can't really say for sure when..

> 2.- Working with big files (700megs) in the RAID comsumes a lot of cpu
> resources, is this normal? I have an Pentium 4, 3Ghz and 1GB RAM...

Probably depends how you define "working".
For simple operations, my *guess* would be that your CPU should
outperform your I/O subsystem, at least if you have DMA enabled.  You
can check if that's the case with 'hdparm /dev/hd<x>'.

I'm not sure how to analyze your CPU problem.  You're probably
interested in knowing whether it's MD doing XOR for raid5 or it's the
kernel busy waiting for your IDE disks.  Unless you are doing other
things, like encryption for example.  Perhaps a tool like 'top' can
help you.  But again, I have no real good idea how to find out. 
Perhaps others can be helpful?

With 8 disks and a standard PCI bus, my guess would be that your PCI
bus would be the first thing to get saturated.
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paul kölle | 1 Jun 2005 21:56
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Cannot boot from initrd into RAID1

Hi list,

well, I won't bother you with the whole story, so just the important
facts. I have to use initrd because I need to preload the module for the
 SATA Controller (4port Marvell). I have 4 disks with /<root> and a few
other partitions on RAID1 and others on RAID5. I made a raidtab config
and build the arrays with no problems, created fstab an can mount all
partitions from my boot/rescue system just fine. The problem is booting
the system. After loading the SATA module, linuxrc tries to mount
/dev/md0 (which is supposed to be /<root>) and fails with input/output
error. ^D -> rescue shell let me do cat /proc/mdstat wich shows
something like:
<identities>  [raid1 raid5]

but no arrays. I wonder if I need a statically built binary of mdadm or
thelike in initrd to initialize the arrays or should a proper configured
kernel just do fine?

thanks
 Paul

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Carlos Knowlton | 2 Jun 2005 17:23

Is there a drive error "retry" parameter?

I want to understand exactly what is going on in the Software RAID 5 
code when a drive is marked "dirty", and booted from the array.  Based 
on what I've read so far, it seems that this happens any time the RAID 
software runs into a read or write error that might have been corrected 
by fsck (if it had been there first).  Is this true?

Is there a "retry" parameter that can be set in the kernel parameters, 
or else in the code itself to prolong the existence of a drive in an 
array before it is considered dirty? 

If so, I would like to increase it in my environment, because it seems 
like I'm losing drives in my array that are often still quite stable.

Thanks!
Carlos Knowlton
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Michael Tokarev | 2 Jun 2005 19:16
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Re: Is there a drive error "retry" parameter?

Carlos Knowlton wrote:
> I want to understand exactly what is going on in the Software RAID 5
> code when a drive is marked "dirty", and booted from the array.  Based
> on what I've read so far, it seems that this happens any time the RAID
> software runs into a read or write error that might have been corrected
> by fsck (if it had been there first).  Is this true?

You're mixing up 2 very different things here.  Very different.

Fsck has nothing to do with raid, per se.  Fsck checks the filesystem
which is on top of a block device (be it a raid array, a disk, or a
loopback device, whatever).  It does not understand/know what is "raid",
at all.  Speaking of raid, the filesystem is an upper-level stuff.  Again,
raid code knows nothing about filesystems or any data it stores.  Also,
filesystem obviously does not know about underlying components of the
raid array where the filesystem resides -- so fsck can NOT "fix" whatever
error happened two layers down the stack (fs, raid, underlying devices).

From the other side, raid code ensures (or tries to, anyway) that any
errors in underlying (components) devices will not propagate to the
upper level (be it a filesystem, database or anything else - raid does
not care what data it stores).  It is here to "hide" whatever errors
may happen on the physical device (disk drive).  Currently, if enouth
drives fails, raid array will be "shut down" so that the upper level
(eg filesystem) can't even access the whole raid array.  Until that
happens, there should be no errors propagated to the filesystem layer,
all such errors will be corrected by raid code, ensuring that it will
read the same data as has been written to it.

> Is there a "retry" parameter that can be set in the kernel parameters,
(Continue reading)

danci | 3 Jun 2005 11:21
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Favicon

Re: Is there a drive error "retry" parameter?

On Thu, 2 Jun 2005, Michael Tokarev wrote:

> Raid code is quite stable and is used in alot of machines all over the
> world.  If you're expiriencing such a weird behaviour, I think it's due
> to some othe problem on your side, and the best would be to find and fix
> the real error, not the symptom.

Sometimes (not very often) a similar thing happens to my server - two of 
the drives are marked faulty (seamingly at the same time).

Fortunately I have always been able to re-construct the array so my data 
was intact (and there was no need for a week of backup restoration), but 
it still is very annoying.

Each time after that happened I tested the failed disks with 'badblocks 
-n', but there were no read/write errors. Unfortunately, libata doesn't 
support SMART (in that version, at least).

To add some details, I'm using a Promise SATA150 TX4 controllers and 4 
Maxtor 6Y200M0 SATA drives for a RAID5 array (holding most of the data). 
Additionally there is an on-board Adaptec AIC-7901A U320 with two IBM 
IC35L073UWDY10-0 for a RAID1 array (holding operating system, homes, ...).

The kernel is 2.6.8-24.11-smp, the OS is SuSE Linux 9.2.

  D.

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(Continue reading)

paul kölle | 4 Jun 2005 19:57
Favicon

Re: Cannot boot from initrd into RAID1[solved]

paul kölle wrote:
> Hi list,
> 
> well, I won't bother you with the whole story, so just the important
> facts. I have to use initrd because I need to preload the module for the
>  SATA Controller (4port Marvell). I have 4 disks with /<root> and a few
> other partitions on RAID1 and others on RAID5. I made a raidtab config
> and build the arrays with no problems, created fstab an can mount all
> partitions from my boot/rescue system just fine. The problem is booting
> the system. After loading the SATA module, linuxrc tries to mount
> /dev/md0 (which is supposed to be /<root>) and fails with input/output
> error. ^D -> rescue shell let me do cat /proc/mdstat wich shows
> something like:
> <identities>  [raid1 raid5]
> 
> but no arrays. I wonder if I need a statically built binary of mdadm or
> thelike in initrd to initialize the arrays or should a proper configured
> kernel just do fine?
replying to myself:

As it turned out the problem is that if RAID support is compiled into
the kernel but the driver for the disk controller is a module the kernel
tries to init the RAID but the disks aren't there yet because the module
is loaded later from the initrd system.

There are two possible solutions:

1. Build all RAID support as modules and make sure the modules are
loaded in the correct order from initrd. Than with partitions set to FD,
the kernel should be able to access the /dev/md* devices (haven't tried
(Continue reading)


Gmane