Topic: Which disk setup for raid?

[ron_uit_best]

Hey all,

I am thinking of installing SME server as my new server distribution. It looks like the best choice, but I have a question.
Nothing has been set up so far, I will have to start from scratch. I have a P3 at 800mhz and I have 5 drives here:
1 SCSI 10k rpm 18GB  (including controller) and 4 drives IDE 20GB

What should I do? Can I profit from the speed of the SCSI drive and make it the boot drive and still have a nice raid config?
And how would that raid config look like? I don't need a lot of room for files. I might add a 80GB laptop drive later if I want
a lot files on it.
Maybe only use 3 drives? or 4? With or without SCSI? any special things to watch out for?

I am totally new to SME, but my linux-life is 1,5 years now (Zenwalk/Slackware), so I am not afraid (I mean: I love) to use the command line.

Any ideas are welcome?

Kind regards, Ron

[imcintyre]

It's my understanding from reading posts here that all the drives in the raid have to be the same size.
http://wiki.contribs.org/Raid


What are you going to do with the server? That should help you decide re disk size. You might be concerned about your disk size and getting too large a disk. You might not be able to virus scan it in a sensible amount of time. I have a 1.8 ghz P4 with 768 ram it takes about 4 hours to scan 46 Gb.

[kevinb]

You could create a custom array by typing "sme partition" at the install prompt.

Then you could have a:
    72 Gb RAID 5 with five 18 Gb partitions on /
    100 Mb RAID 1 with four 100 Mb partitions on /boot
    with what ever is left over (4x ~1.9 Gb): RAID 5 swap partition on /swap

Kevin

[ron_uit_best]

@imcintyre: Don't ask where, but somewhere in the forums/docs I read that since 7.3 there is no need anymore for using the same disks and types and sizes. The server is going to be an email and webserver; email for private use and webmail and the webserver to host 1 or 2 sites with very few visitors. But I also want my files accessible and backed up, so maybe not now but later for sure it will have to act as an ftp server as well.

@kevinb: sounds like a nice setup, but what happens if a disk fails? Can I always read a disk from another machine in case the whole pc fails? And does SME automatically pick the SCSI as the boot device?

Kind regards, Ron

[kevinb]

I have manually partitioned with mixed drives and had it work.

Mr Heck,

In what I laid out your SCSI would be holding 25% of your data only. If it fails you would have to replace it with another disk the same size or larger and manually resync it (http://wiki.contribs.org/Raid#Resynchronising_a_Failed_RAID).

The four IDE drives will have the all the /boot and /swap partitions along with the other 75% of your data. If you loose a IDE drive you will have to replace it with the same or larger also and resync it.

SME will "boot" from any of the four IDE drives only.

You can only loose one hard drive and keep running soothly. Since the /boot partition is mirrored across the four IDE drives you can loose the SCSI and three IDE drives and the system will stil boot to the kernel (that is realy not much help .. do good backups).

The only way you can read the disk from another machine is to move all the drives, keep them in the same order, and boot from them. I have never tried mounting a software RAID after moving it to another computer ... may be possible ... in theory.

If you are strapped for hardware you may want to use the SCSI and two IDE (on different channels for best performance) as a RAID 5 (36 Gb) with the /boot and /swap as RAID 1 and RAID 0 respectively on the same two IDE drives ... and .... use the two remaining IDE drives in a RAID 0 (40 Gb) for a backup drive and use AFFA to backup.

Let us know how it works out.

Kevin

[ron_uit_best]

Tnx Kevin,

Your last option sounds very nice and understandable. A 3-disk RAID 5 and maybe later add the 2 other disks. If I understand correctly from your first post and the docs is that I would have to use 'sme partition' or else SME will use the 3 disks as Raid1+hot spare, while raid 5 sounds nicer.

I will built the pc this way and give it a try.

Ron

[kevinb]

If you disconnect the two IDE drives that you are going use as backup you can install SME with "sme nospare" and get a three disk RAID 5. But you will not be using the extra 2 Gb on the two IDE drives (no big deal and much simpler than "sme partition"). After the install is complete reconnect the two IDE drives an manually create a RAID 0 with them. Google "create RAID array Centos command line" to find the step by step instructions for this.

[ron_uit_best]

Hey,

Took some time, because the pc was not cooperating. First I could not get the SCSI in the case, so I moved the whole system (compaq) into another bigger case, but then I had to find a way to make the power button work (different plugs). After that the whole thing beeped 3 times. Bad memory as it seemed, while I thought it was the video that was bad.
Now it works, SME installed fine with no spare. I have (according to Raid status) a working Raid5. Soon I will configure the whole thing and replace the old server and router.
First I have some exams to study for. Thanks for helping. The other IDE drives I have left out: I noticed they were not 7200 rpm, so I will wait until I am in need of this space.

Ron