SOFTWARE RAID: lot of troubles !!!

[flashbios]

After some heavy testing I found out that Zentyal (or lets's say UBUNTU) has serious troubles with SOFTWARE RAID...

Normally I use 4 (!) equal harddisks which are in RAID1 (mirror) as my DATA-DISK set.
If I shutdown the server and disconnect 1 disk, the server must be detect the problem and automatically start again with one harddisk less.
As soon there is a new hardddisk added, the administrator must have the option to add this new disk to the RAID.

(With ClearOS (Centos based) I used WEBMIN to add the new drive to the raid, also possible in Zentyal (after installing MDADM))

But as soon you disconnect a drive from the raid1, the system doesn't start normally.  You must do a lot of unneeded things to get the system alive again !

I really like Zentyal, but dataprotection is the most importent thing of a server.

So, I hope this is something what can be fixed very easy (I remove one harddisk for a new one every month to have a complete backup of all the data on a harddisk not connected to the server), but after searching the internet this seems to be a non-solved issue from UBUNTU Linux...

Clearos and Centos has no problem with this at all.

A hardware-raid is faster, but if the raid-controller fails, you have serious problems to get the data back... So, not the right sollution..

[ichat]

like you said, if this is a ubuntu problem,  try and post it upstream in the ubuntu forums,  there may allready be work arrounds for it, or even software to solve this issue.  since the ubuntu community as a whole is lots bigger than the zentyal one its more likely that you get diferent comments and helpfull links.

eventually you could  add a feature request to include one of more of those solutions...

[flashbios]

Switched back to ClearOS again, very stable system (centos).
And perfect software-raid functionality inside...

But I will allways keep a look at zentyal: great system but it should run with CENTOS or REDHAT, not ubuntu..

It's a pitty, but a good and very stable software-raid system is essential...

I hope that the Zentyal company can fix this HUGE problem..

[ichat]

flashbios, that will not even happen when hell freezes over,  and im verry gratefull for that,

the opensource versions of redhad (fedora and centos) are verry poorly maintained,  and clearos to me looks verry mutch like a desaster ...  if  ubuntu doens't work well in certain cases that should be fixed...  but i haven't noticed your errors at all and ive been using debian and ubuntu from the time that redhad didn't even have community siblings.   

I hope that the Zentyal company can fix this HUGE problem.. --

sorry but i must strongly disagree as in my (long) experience with adminstration of servers, the biggest problem with a server is allways its administrator.

i would state that 'huge problem' is at least a verry big overstatement... 

[flashbios]

That's your opinion ;-)   We can discuss this all, but that's useless: some people like the color blue and other peoples don't..

If you use software-raid and have a couple of datadisks (2, 3 or more) which you are using to keep all the data - it's very nice if you can remove 1 disk and exchange it with another disk without a lot of trouble to get the server running again.  this is very handy if you want to keep a harddisk with all the data on a safe place (backup). And no waste of time.

Linux-distro's like CENTOS have no troubles with that all all.
So, maybe you would test this all by yourself (you seem to be an expert) and try to fix the problem: this for all Zentyal users and ofcourse the Zentyal company ;-)

Anyway, thanks for your posting !

[christian]

I tend to agree with ichat on this point: 95% of IT problems lie between keyboard and seat 

Then we could compare Ubuntu vs. RedHat, CentOS or Debian, difference is very minimum and debate very probably endless. It's more a matter of habits and at the end, of religion.

What you can't do it to compare CentOS and Zentyal and, on top of this, to ask Zentyal team to solve something that should be covered, assuming there is an issue, at OS level.
Back to my initial point: do you really think CentOS differs from Ubuntu or RedHat:
https://help.ubuntu.com/10.04/serverguide/C/advanced-installation.html
https://help.ubuntu.com/community/Installation/SoftwareRAID

Then you may prefer the way CentOs deals with this, compared to Ubuntu. I'm not discussing this. This is your choice. but again, why do you think this has to be covered by Zentyal: it's pure OS stuff.
And if definitely this is key element for you, I think you made the right choice while switching to ClearOs because it runs on CentOS. No problem with this assuming you do not mix-up everything putting debate at Zentyal level 

[flashbios]

Thanks for the links, got that info already. 
If you want to swap data-disks on a regulair basis, then it's not a very handy way.
Centos and RedHat handles this better, but maybe ubtuntu will get this improved later too ;-) 

[Reinhold]

After some heavy testing I found out that Zentyal (or lets's say UBUNTU) has serious troubles with SOFTWARE RAID...

Normally I use 4 (!) equal harddisks which are in RAID1 (mirror) as my DATA-DISK set.
If I shutdown the server and disconnect 1 disk, the server must be detect the problem and automatically start again with one harddisk less.

...works for me with Zentyal ... works exactly as described ;-)
Seems to me that you have a partitioning / boot problem...
Linux Softraid (mdadm) is partition based so you need an active boot partition on both disks in addition to your raid1 md
... just make those NOT UNNECESSARY steps
(Also: define another, a 3rd, disk as "spare" - you won't even have to "add" it when it's needed)
<smile>

Regards
Reinhold
...who wonders what your 4th disk might be for ... ;-)

[christian]

I feel that flashbios is using mirroring as backup strategy 

Although this approach is often used on larger systems, it also comes with scripts to ensure that all write operations are frozen at the time you synchronize disks then stop mirroring before you release writes. This is, f.i. required to ensure consistency among various files or DB.
Is it still fitting with SMB strategy  I don't think so.
Mirroring (or almost any RAID of your choice) for data protection is OK.
RAID 1 as back-up strategy is a very different animal  and if this is required in order to manage sensitive data, I would rather go for dedicated storage OS (like FreeNAS) and mount volumes exposed via Samba. Well... my own personal choice only, of course   

[flashbios]

I feel that flashbios is using mirroring as backup strategy 

Although this approach is often used on larger systems, it also comes with scripts to ensure that all write operations are frozen at the time you synchronize disks then stop mirroring before you release writes. This is, f.i. required to ensure consistency among various files or DB.
Is it still fitting with SMB strategy  I don't think so.
Mirroring (or almost any RAID of your choice) for data protection is OK.
RAID 1 as back-up strategy is a very different animal  and if this is required in order to manage sensitive data, I would rather go for dedicated storage OS (like FreeNAS) and mount volumes exposed via Samba. Well... my own personal choice only, of course   

Thanks for the info ;-)
All the data-disks contains 1 Linux RAID-partition, nothing else.  I can stop the server, disconnect a datadisk and reboot the system again.
It doesn't matter which datadisk, as long there is still 1 left. Normal startup, all data is direct available.  I can change a damaged disk, or return a disk (used as backup_ in the server
and add it again to the mirror.  With centos, this all is working very easy.  Ofcourse, a mirror is not a backup system: I store disks on a safe place with all the data (like a snapshot), and I allways keep a couple of disks in this way..  (different backup-sets).  Like what we do with tape-backups, but it's too much data for a tape ;-)  (or I must by a reall expensive system).
Also I make backups to and another live backup-system, I lost a lot of data long time agoo, don't want to have that again ever...
Maybe this all is not the best way, but it works for me now for a few years without problems ;-)

Anyway, the same thing I want to do with ubuntu (zentyall 64bits): after heavy testing, it failed more then ones..
With centos, rebuilding etc. is just a few clicks at the WEBMIN RAID option, system starts allways.  With ubuntu: It doesn't, too much hazzle to get it running again..
Possible my poor experience and knowledge of Ubuntu, I will try it again later if somebody can tell me what's wrong and how to fix it..

Ok, back to work.... 

[ASRIX]

Well... as christian said, this is all about Religion... personal choices and opinions.

I think Linux Software Raid is a great solution. In Ubuntu, we have had to replace disks in several times, and got no problem with that. In those servers that Zentyal is installed, we receive the information of a failure of any disk and then deal with the problem.

May be Zentyal can have more things to manage RAID stuff, but it still be a problem of OS.

And, in the other hand, the Ubuntu's community is very active, and you can have a lot of information of practically any thing, just via google. I don't know how is this working now with CentOS or Fedora, but we tried it some time ago, and encountered a lot of trouble with that.

That's just my opinion. Linux RAID software works ok, just need to be managed. And Ubuntu works ok with it too.

One final opinion... sorry for my english!