Slackware 13.1 hardware raid
 

Hi all, I will soon be installing Slackware 13.1 on a (file) server here at work. The server will use hardware raid, using an Adaptec card. I've never worked with hardware raid before, is there anything I need to know before I install? Software I need to include or exclude? Should the necessary drivers be included out of the box? Will I have to do any setup or configuration of the raid, or will the hardware just kind of do its thing?

I set up a software raid about a year ago, and it was a bit of a headache.. I assume hardware is simpler, but I have no experience. Any advice is appreciated!

Yeah, don't do it.

That's a bit over the top, but you need to consider that many hardware RAID controllers create RAID devices that can be used by only that type of hardware RAID card. Since that's an Adaptec card, that probably won't be much of a problem; however, it isn't a problem that you have with software RAID.

I'm sure the Adaptec site would have documentation on whatever specific card you are going to use.

I've found software RAID to work for my needs, but my needs didn't include running a file server at work. :-) (I do run one at home, but I expect the demand there is much less than your server will have to handle.)

If it's really hardware RAID, then it should be recognized as a single drive and no further work on your part should be necessary.

That's what I was hoping.. thanks.

Unfortunately that's not really an option at this point. I didn't have any say in the hardware setup.. the equipment was purchased, and I was asked to install linux on it.

I don't understand what you mean. We already have the hardware pieces, which presumably will all be compatible with each other. At least I hope so, otherwise someone made some poor choices when purchasing it..

This is for our video team, who eat TBs for breakfast. We've had software raid running for a year now, and the initial sync took about a day and a half. Don't know if hardware raid will improve that situation, but it seems like it will simplify things overall.

I agree with Richard Cranium. I find myself exactly in trouble with a HP Proliant Hardware RAID, when I was changing Operating System from Suse to Slackware (it is possible its not true hardware RAID). I had two hard drives in one mirrored ARRAY which was configured by a BIOS utility. It was alive for two years with lots of data on it.
I removed the hard drives and replaced them with new drives (where the new OS should go and used mdadm software RAID). I leave the old drives intact for possibility of later needs. Since I removed the old drives I was not able to access the data again.
What is the worst in my case - I was used to put the drive with existing data into another PC where I just mount it by Slackware and can access everything I need on the existing partition. In this case I was not able to do that. I see only empty space on the drive. I was able to access data only when it was connected to the original RAID driver in HP Proliant. Finally I was not able access them at all. The BIOS utility showed me that the driver "port" was changed and the ARRAY is not "HEALTHY" - it cannot be repaired. I don't know, maybe I did used that RAID (utility) incorrectly but at that moment I was decided to try software RAID.
Another thing was error reporting on drives. In cease a faulty drive I was not noticed about it.
Now I use linux software RAID by mdadm, I setup notification by Webmin where the status of drives are monitored and when one drive goes wrong I am noticed by email. I also recovered successfully one bad hard drive in my RAID devices.
I am really satisfied with mdadm. My personal experience is that your chances with linux software RAID are considerably higher.
It seems to me that it is lot more flexible then the previous hardware RAID provided by the motherboard. Only just for share my experience.

Well, I don't know what Adaptec card you are using that provides hardware RAID. There is a greater than zero chance that whatever metadata is written onto the drives used to constitute the RAID device(s) will only work with that particular Adaptec card.

Do NOT assume otherwise.

If the Adaptec web site tells you otherwise, then you can almost certainly believe them, but do not believe that you can use software RAID or another vendor's card to recreate your RAID arrays unless there is documentation telling you that such things are possible.

Thanks for the heads up. Unfortunately I don't have as much control over the situation as following your advice would require. I was not involved in or consulted on the purchasing of the hardware, I was just told to install linux on it. It's been purchased, the decision was made, it's done. I'll let them know about the potential limitations, but other than that it's not my problem. My problem is to make it work. Then I go back to my regular job (which has nothing to do with server administration). I just happen to be the only one here with considerable linux knowledge.

So it sounds like it'll work fine - as easily as any other drive - but replacing the drives in the future could be an issue. Does that sound right?

Thanks for your advice :)

This is what the Adaptec site says about the card we have:

The part in bold indicates that we shouldn't have a problem replacing the drives, correct?

Thanks.

Having run a number of Dell PE systems, I am somewhat of a fan of a solid hardware RAID but I have never had the opportunity to try Linux on such a machine. If you are setting up a new system then you should have no problem, provided the modules are available. Container setup will be in the card BIOS and the resulting drive(s) will show as sdax, sdbx and so on. If you are trying to use an existing system with a new RAID card, you will likely not be able to recover anything of the former system and may find the disks unusable. My policy has always been to backup data and migrate a system if a change in RAID is required. Like I say, my experience had been exclusively Windows Server (pre-2003) but I prefer hardware RAID over software, at least in the arena of server machines.

Replacing the drives should never be a problem. What will you do when, not if, the card fails and you need that data yesterday. Hope you have a spare. With software raid, should the system suffer a catastrophic failure, to gain access to the data, connect the drives to any (well just about ;)) Linux system, and you'll have access to the data. With hardware RAID you'll need another card that is compatible with the one you currently have. Could mean the same model, and/or same firmware, and/or same bios version.

If you're hell bent on using hardware raid, and have a legit reason for needing hardware raid over software raid, order a spare card now, before the array is even active. Hardware raid does have its advantage in some applications with some cards. It's up to you do the research if the pros outweigh the cons. Be sure to check benchmarks of that card against benchmarks of Linux software raid.

I am not hell bent on doing anything other than making this server work so I can go back to my real job and get my real work done, which has absolutely nothing to do with hardware or server administration.

Again, the decisions are not mine to make, potential data loss is not my problem, I don't have the authority to order a spare card, server administration is not my job and the hardware was already purchased without my knowledge or consultation.

I'd welcome any helpful advice about setting Slackware up with hardware raid, but (everyone) please stop telling me to do something I have no control over. Hardware raid is being used, end of story.

The install itself should be pretty straight forward with the raid array showing up as a normal single device.

Just set up the array first (with the BIOS utility) and then continue with the install as normal.
If the drives show up separately (or not at all) then you may need to build a custom install kernel/initrd.

I'd just be sure to let the purchaser know of the limitations mentioned above and make sure there are adequate backups in case the raid card fails.

If you always treat raid as a form of redundancy and not as a "Backup Method" you'll be just fine.

You can always replace the drives.

It's the bleeping card that's the problem. Have the genius that is forcing you to use hardware RAID ask Adaptec what other cards can be used to replace the one that you intend to use if the card that you currently have fries/fails.

If the answer is "just buy another one of the same model", then the potential data loss is on said genius. Make sure he CCs you with that answer so when they start looking at your ass when the something goes bad, you will have something to show "hey, I warned genius person over there".

I have talked to too many friends who had used hardware RAID using a controller on the motherboard and found to their chagrin that they had to replace the failed motherboard with the exact same model to get their RAID arrays to reconstitute. (Or buy a controller card that matched the RAID controller on the original motherboard.)

I've got 4 machines around here with hardware capable RAID controllers. Every RAID device in my house is software RAID. The CPU hit is negligible with my Adaptec AIC-7892A U160/m (rev 02) and my nVidia Corporation MCP78S [GeForce 8200] SATA Controller (non-AHCI mode) (rev a2) controllers.

My thinking is that if the drives show separately then the RAID has not been set up properly. By the time the machine 'sees' the drives, they are already in a container. As long as the kernel modules load at boot you should certainly see the drive(s) (multiple if you have set up more than one container) and the install will follow normal procedure from that point. If you do not have the kernel modules you will either see an inaccurate representation of the RAID card or nothing at all. It seems to me that most, if not all, Adaptec hardware is supported in Linux so it will be only a matter of booting a huge or custom kernel or getting the proper modules into initrd. I use an AHA-2940U2 SCSI and if I don't include the module at boot you wouldn't believe what it can do to the IDE discovery.

To be honest, I have only used Dell PERC 2/3 si/sc/dc RAID setups but after many years of service I have never had one fail. Also - more honesty - I have never neglected DLT backups at regular intervals, just to be safe.

One thing - before attempting Slackware, be certain that the Adaptec cards that you will be using are supported. If you need more detail about setting up containers, we can help with that too.