Topic: raid on smeserver with bios raid set

[xsel]

Hello

I want to use an intel board with mirror raid setup in the bios.
I remember that smeserver deletes ALL hdd's on install, so I want to
1st install 1 hdd and install smeserver,then install 2nd hdd and hopefully
the bios raid feature on the intel board will ensure that mirroring takes place.

I plan on installing smeserver 7.4 beta1 which I have been using a short while with no issues. I installed sarg,and awstats and the updated sme backup module(backup to lan),plus fetchmail,which are the only extras that will go onto this server.

If I am wrong on this, how does smeserver do its raid,because I dont want stripes.

Some background:
A customer had 7.1 with raid which kept bombing out.The raid was removed,I suppose with a complete new install.This setup 3 years back at least,and still running 7.1-too scared to upgrade to 7.3 ..
I did not install or setup that smeserver,I only had to maintain the shares,and network connections,so that is how I started to learn about smeserver,coming from a windoze MCSE background.

Thanx/Pete

[Stefano]

Hi

if your raid controller is not a REAL hw raid controller, then forget about it and let SME do his raid

SW raid is very stable.

HTH
Ciao
Stefano

[xsel]

Hi

regarding SW raid with 2 hdd's, what happens when 1 hdd bombs?
Just stick in a replacement and restart?

or can smeserver do a 3 hdd SW raid thingy?

Which would be best, as I really need a rock solid backup/redundancy feature here, for the customers emails mostly,but why not save everything hey.

Thanx/Pete

[Stefano]

Hi

regarding SW raid with 2 hdd's, what happens when 1 hdd bombs?

SW raid with 2 hd is raid1, i.e. mirroring.. if one hd fails, a mail is sent to admin and server continue its work in degraded mode

Just stick in a replacement and restart?

you'll have to replace failed hd (how depends to your HW..), then go to console and use "Manage redudancy disk" menu point to add the new hd to raid array

or can smeserver do a 3 hdd SW raid thingy?

if you install SME with 3 hds, it will be setup with raid1 with a spare disk, should one fails, the spare one will immediately be inserted and re-synced

Which would be best, as I really need a rock solid backup/redundancy feature here, for the customers emails mostly,but why not save everything hey.

Thanx/Pete

with raid1 (better with 3 hds) you have continuity.. raid is not backup.. for backup feature you need a tape or another disk..

Please, to understand how SME's raid and backup feature work, read carefully the documentation

HTH
ciao
Stefano

[Tib]

Hi

regarding SW raid with 2 hdd's, what happens when 1 hdd bombs?
Just stick in a replacement and restart?

or can smeserver do a 3 hdd SW raid thingy?

Which would be best, as I really need a rock solid backup/redundancy feature here, for the customers emails mostly,but why not save everything hey.

Thanx/Pete

3hdd software raid thingy is called raid 5 ... and yes it can be done.

I personally run a raid 5 with 6 drives using hardware raid and just setup SME ask a one disk install ... that way the hardware controls the re syncing when a hdd is replaced.

I have also tried the software raid 5 that SME does and it works well.

All depends on the hardware you have and what you are really after.

Regards,

Tib

[Stefano]

3hdd software raid thingy is called raid 5 ... and yes it can be done.

this is not correct on SME..

if you setup SME with 3 hds, it will setup a raid1 + spare array..

if you pass the option "--no-spare" (or similar) then, AFAIR, you should have a raid5.. but raid5 with only 3 hds is, IMHO, evil

Ciao
Stefano

[Tib]

this is not correct on SME..

if you setup SME with 3 hds, it will setup a raid1 + spare array..

if you pass the option "--no-spare" (or similar) then, AFAIR, you should have a raid5.. but raid5 with only 3 hds is, IMHO, evil

Ciao
Stefano

Maybe thats the case with SME now ... but you only need 3 drives to start using a raid 5 ... and you don't loose 50% of your space that way.

So in essence you can setup a raid 5 with 3 drives in SME with the correct commands.

General rule with raid 5 is you loose one drive there abouts ... you will retain 66 - 75% of you drive space.

Best thing to do is read up on raids before you decide on what you will do.

There is a lot to know about raids ... eg: best to use 3 or more identical drives for a raid 5 etc.

Regards,

Tib

[Reinhold]

.. but raid5 with only 3 hds is, IMHO, evil

Stefano,

That's NEWS ... and not only to me 

i) capacity with 3 HDs:    raid1+ -> 1 HD  raid5 -> 2HD   iow DOUBLE CAPACITY! -> HALF THE COST!
ii) (in general soft-) Raid1 will be SLOWER than 1HD (write). RAID5 with a decent CPU and 3x HD buffer mostly is faster (!) - check!
iii) I (we) sure like to USE hardware we've PAID for! IMHO a spare should sit on the distributors shelf instead of in one of our cases!
iv) the 'spare' will consume energy, produce heat and (often) die right after one of the working Raid1 disks - almost virgin 
v) Buying a spare (replacement?!) when you get the "failed" message isn't "too late". You just run in degraded mode - so what - 90% of the world runs "a single HD" which iow is "degraded mode". If you do panic you can always turn off the machine asap ... Personally I rely on backups so Raid1 or Raid5 will be turned off when I get the new HD (latest next day for me).
vi) a newly bought HD will have years of warranty ... and once you get back the/a refurbished/repaired HD ... you do have a FREE SPARE for your shelf too -> minimal downtime.

Regards
Reinhold

[mercyh]

the only problem with buying a spare later is that usually drives last years. When the old XXgb drive goes down and you need an exact replacement it may be hard to find.

[Stefano]

Stefano,

That's NEWS ... and not only to me 

i) capacity with 3 HDs:    raid1+ -> 1 HD  raid5 -> 2HD   iow DOUBLE CAPACITY! -> HALF THE COST!
ii) (in general soft-) Raid1 will be SLOWER than 1HD (write). RAID5 with a decent CPU and 3x HD buffer mostly is faster (!) - check!
iii) I (we) sure like to USE hardware we've PAID for! IMHO a spare should sit on the distributors shelf instead of in one of our cases!
iv) the 'spare' will consume energy, produce heat and (often) die right after one of the working Raid1 disks - almost virgin 
v) Buying a spare (replacement?!) when you get the "failed" message isn't "too late". You just run in degraded mode - so what - 90% of the world runs "a single HD" which iow is "degraded mode". If you do panic you can always turn off the machine asap ... Personally I rely on backups so Raid1 or Raid5 will be turned off when I get the new HD (latest next day for me).
vi) a newly bought HD will have years of warranty ... and once you get back the/a refurbished/repaired HD ... you do have a FREE SPARE for your shelf too -> minimal downtime.

Regards
Reinhold

Reinhold, the points you show are indeed true but:
- if I have to work with SW raid, I will use raid1.. I can always put one of the array's hd on another server and my data is there..
- Viceversa, should I have to work with HW raid, well, raid5 is definitely the way.. but only with 3 (or more) hd and at least one spare..

BTW, OP asked for a 3 hd solution with redudancy/security.. in this case, raid1 + spare is the only solution, because murphy's law is there, just around the corner.

Ciao
Stefano

[Reinhold]

the only problem with buying a spare later is that usually drives last years. When the old XXgb drive goes down and you need an exact replacement it may be hard to find.

mercyh,

  Welcome to the beauty of Linux Softraid...
Being PARTITION BASED you only need to make A PARTITION OF SAME SIZE...
Linux/mdadm really doesn't care that/if you leave 20,30,50% of your new HD unused.

I know that "we" (=meto) tell you that you "should use" an exact replacement but in reality you don't.
ANY HD that is larger than the failed one should do...should serve as "replacement" drive.
(Fair)Warning: Please make yourself knowledgeable if you decide to go this way ... google is your friend!
(It ain't rocket science however - it WILL WORK  )

Regards
Reinhold

P.S.: Now try that with an "extremely expensive" or "ridiculously rare" (fake) raid hardware.
iow ... (when) using a raid-controller we always buy (at least) one spare...
(guess why you can sometimes get "slightly old models" "unused" at ebay)

[mercyh]

Linux/mdadm really doesn't care that/if you leave 20,30,50% of your new HD unused.

I actually knew that but hadn't thought of it in the way you explained it.

readjusting thinking to (I hope) a better way of doing raid...................

Thanks for the great tip.