Topic: RAID for SME 6.0beta2

[Brent]

I just bought a Compaq Proliant 6500 (quad PIII 500mHz, 1GB RAM, etc) and I want to install SME 6.0beta2 on it.  I already have the ISO image and boot floppy, and it's no problem for me to install the sofware onto my machine.  However, I don't have the first clue on how to set this up to use all 5 of my 4.3GB drives as a RAID array.  I'm familiar with most functions of Win2KP, but I've never used Linux before.  I do have some experience with SME 5.6, tho as we run that for a mail server at work.  I did not perform the installation, but I do know that machine only has 2 drives.

Are there any good step-by-step-cuz-I-don't-know-Linux-worth-beans articles out there that will help me to get this running the way I want?  Right now I have the machine set up to only use one drive.  Help??

[Ray Mitchell]

Brent
sme is designed to configure 2 (matching) drives in a RAID1 array.
If you want more drives in an array then you need to manually configure them after you have done a RAID1 instal using only 2 drives.
Do not even connect more than 2 drives for the first instal, connect them after you have done the RAID1 instal.

As far as how to do it, you are on your own, there have been some references in these forums to multiple drive setups, but I cannot recall a specific one for your needs. Search for RAID1 all dates.

You may also like to read this link and the Related References on that page for further info
http://linas.org/linux/raid.html

Regards
Ray

[Kelvin]

Brent,

You have not mentioned if your Compaq Server had a hardware RAID controller in it or not. If it does and your hard disks are connected to it, you need to :-

1. Check if the controller is supported by SME6.0b2
If not stop.

2. If so, confirm that the controller is supported as a RAID controller and not just a drive controller.
If not stop.

If so,
2. Use the Compaq Smartstart utilities to configure the drives as a RAID 5 (or whatever RAID level you want) pack.

3. After that, boot up off the SME 6 CD and begin installation.

Good luck !

Kelvin

[Ray Mitchell]

> sme is designed to configure 2 (matching) drives in a RAID1
> array.

I was referring to software RAID1, if you have a suitable hardware card  to do the job then that's a different matter.

Regards
Ray

[Ergin Özdemir]

You would have to creat one Array with Compaq SmartStart CD, after that choose Single Harddisk installation and it runs smoothly.

[Brent]

I have determined that my Compaq does not have a RAID controller in it.  This now seems to become a case of either a) installing a supported RAID controller and then installing SME as a single-disk installation, b) installing SME as a RAID1 configuration and leave the other drives as spares, or c) try fiddling with the Linux kernel to set up a software RAID.

Since I'm Linux-deficient, I'll likely go with route a) or b) unless there are other ideas to be had.

Thanks for all of your quick responses to my query.  It's this sort of assistance and community that makes open source software such an appealing alternative to traditional (read: Microsoft) approaches.

[Ed Form]

Brent wrote:
>
> I have determined that my Compaq does not have a RAID
> controller in it.  This now seems to become a case of either
> a) installing a supported RAID controller and then installing
> SME as a single-disk installation, b) installing SME as a
> RAID1 configuration and leave the other drives as spares, or
> c) try fiddling with the Linux kernel to set up a software
> RAID.
>
> Since I'm Linux-deficient, I'll likely go with route a) or b)
> unless there are other ideas to be had.

The system doesn't require you to fiddle with the kernel to get software raid. Just install two identical hard disks, preferably each as the master on one of the two standard IDE controllers, and accept the option to make a software raid during installation. That's it!

You can only have two disks, and you can only mirror them. Striping and stripe/mirror hybrids are not provided by SME because they are not particularly safe. With the two discs as masters on separate controllers it is difficult to measure any difference in performance from running on a single hard disk. If you run the two discs as master and slave on a single controller the performance hit is typically 5-7%.

Ed Form
Ed Form

[James Pybus]

The simplest way I can think of would be to install the standard Raid1 install, then setup the other 3 drives with Raid0 or Raid5 using software Raid already on SME.

You can then copy all your info from home to the new raid and mount it as home.

HTH
James

[Dan Brown]

Ed, that would be option (b) from his post.  Linux supports software RAID 5, but setting that up would take quite a bit more work.  I don't think the concern is so much safety as simplicity and performance.

[Kelvin]

Hi Brent,

Personal Opinion :-

You've already spent money on a good hardware base for your server. If your hard drives are in the standard Compaq Hot-plug carriers, adding a supported hardware RAID card will also give you the advantage of :-

1. Hot-Swap support
2. Automagic RAID recovery upon hard disk replacement (no need to remember commands to rebuild array - given that your background is Windows)
3. Zero-downtime if you don't suffer multiple drive failures (enough to cripple the RAID pack)

Cheers,

Kelvin

[Brent]

Kelvin,

I've found a Smart Array 221 RAID Controller in my area and I'm planning to install that.  From my noodling around on their website, there appears to be a Linux driver for this controller.  I'm not sure if it has to be supported by SME 6.0b2 itself, or just Linux, but I'm supposing that provided Linux supports it, SME will, too.

I like the features that the hardware RAID provides so I think it's definitely worth pursuing.

[Brent]

Oh.. one more quick thing...

After opening the hood, it appears as though all 5 drives connect to the mainboard via one SCSI cable.  I'm assuming that EACH drive will have to connect the the RAID controller individually, meaning I will have to obtain more SCSI cables and find a way to route them to the controller.  Is this right?

Can you tell I'm not totally familiar with production server architecture?  Especially SCSI?

[Dan Brown]

Nope, one cable will suffice due to the way SCSI works.

[Kelvin]

Hi Brent,

If the Smartarray 221 is a single channel controller (sorry, can't remember, been awhile since I played with the 221), then one cable will do (you don't have a choice ). If the 221 is a dual or triple channel controller, then you can split up the number of drives you have over the number of channels you have to provide additional redundancy / bandwidth.

Kelvin

[Ed Form]

Dan Brown wrote:
>
> Ed, that would be option (b) from his post.  Linux supports
> software RAID 5, but setting that up would take quite a bit
> more work.  I don't think the concern is so much safety as
> simplicity and performance.

I misunderstood what Brent said but, when I commented on Software RAID beyond the SME standard mirror setup I was recalling two messages.

The first was...

*********
Author: Kelvin (forums_AT_quasarsoft.com.au)
Date:   03-19-02 14:53

Personally, if I were using RAID of any sort at all, it would be for the purpose of safeguarding my data, not for performance, otherwise I'd stripe the drives or go RAID 5 with a more upspec controller - something that the current software RAID cannot do. Even if software RAID could do RAID 5 I doubt very much that it can match the performance of a dedicated RAID 5 controller. It is simpler to manage failed drives, reimaging, etc. using a hardware controller than software as well.
*********

And the second was...

*********
Author: Gordon Rowell (gordonr_AT_e-smith.com)
Date:   03-28-01 07:31

Stephan Goeldi wrote:
> > [Gordon Rowell]
> > We don't ever plan to support ..... [software] RAID5
>
> Why not? Is there a big difference in supporting RAID1 or
> RAID5?

To quote Peter Green from the devinfo list:
Only use RAID0 when your data is worthless. Only use RAID5 (software) when your CPU/performance is worthless.

RAID5 is a performance killer. It turns nice fast disks into very slow ones. It is a great idea when you have a cache between your system and the disks, but a very bad idea if your system has to monitor every read/modify/write cycle.

The system overhead of mirroring is less than 10%, and in fact may improve throughput in some circumstances. The overhead of RAID5 is more like 30-35% and gets far worse as the write ratio increases.
*********

Ed Form