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Obsolete Releases => SME Server 9.x => Topic started by: stephdl on May 11, 2014, 08:55:26 PM

Title: sme9 and raid hardware
Post by: stephdl on May 11, 2014, 08:55:26 PM
Hi

I come here to have some feedbacks on raid hardware because with sme9 we will have a /boot which will always use  RAID even when raid=none is given.

In other words is it possible to do a software raid on a hardware raid controller ?

see the bug http://bugs.contribs.org/show_bug.cgi?id=8369 which is the bug opened to fill the documentation.

Using raid=none.
sda1-md0 is for /boot.
sda2-dm-0 for /
sda2-dm-1 for [SWAP]
Title: Re: sme9 and raid hardware
Post by: Daniel B. on May 11, 2014, 09:10:24 PM
Yes, no problem (even if uneeded). The system sees the hardware RAID array as a single disk, and you can assemble soft RAID on top of it. I'm using it on a few servers (backups stored on a HW RAID + soft RAID to make it easier to copy data on external disks)
Title: Re: sme9 and raid hardware
Post by: Jáder on May 14, 2014, 01:04:17 PM
Hi Daniel,
I'm sure you have it working, but I've seen here on forums several uses with problem because they have HW RAID on motherboard and do not use CLI options to do not use RAID.

I allways suggest to use ONLY one RAID type ( SW ) unless you have a REALLY GOOD (and expensive) RAID array controller (those from BIG names like DELL, HP, ...) that DO NOT NEED ANY drivers loaded. The RAID must present all disk to OS just like one without any SW driver.

I think unless you have a underpowered server (low CPU is hard to find today) anyone using less than 6 disks should avoid to buy HW RAID (and use that money to buy memory).
Title: Re: sme9 and raid hardware
Post by: Daniel B. on May 14, 2014, 01:10:01 PM
Of course, I'm talking about real RAID controlers, not FakeRAID (which are just bad software RAID). For the HW vs SW, it depends on a lot of stuff, both have advantages, but HW RAID with a good controler, good write back cache and a BBU will always have better performance. Anyway, here, we're talking only about the /boot partition (because actually /boot is always made as SW RAID in SME9, no matter which option you pass to the installer), for which performance is irrelevant.
Title: Re: sme9 and raid hardware
Post by: stephdl on May 14, 2014, 02:51:24 PM
the installer give 'nodmraid' for all boot option  which is for me done to avoid fake raid on motherboard, i'm right ?
Title: Re: sme9 and raid hardware
Post by: Daniel B. on May 14, 2014, 02:52:54 PM
yes, fakeRAID will always be disabled as the no dmraid option is passed. But /boot is still created as a linux software RAID, even if raid=none is selected
Title: Re: sme9 and raid hardware
Post by: stephdl on May 14, 2014, 03:34:27 PM
Quote from: Daniel B. on May 14, 2014, 02:52:54 PM
yes, fakeRAID will always be disabled as the no dmraid option is passed. But /boot is still created as a linux software RAID, even if raid=none is selected
I agree, 'nodmraid' would say that there is no fakeraid but the /boot will be always on software raid.

I want to close the bug report, once it is done, could be nice more eyes on it to verify.