Has anyone had any bad experiences with Linux software "RAID"?

I've been experimenting lately with Promise ATA-RAID (the "driver based crap) and 3ware Escalade ATA-RAID (hardware based) controllers, but the experiences have not been anything spectacular.
Promise does not deliver at all, in the sense of reliability and 3ware Escalade somehow does not perform well in speed tests, especially on the FreeBSD 4.X platform.

So as one of the alternatives we've been starting to look at Linux kernel based RAID.
My tests so far have shown no problems at all, which makes a paranoid person like me a little nervous :) . I'd like to deal with possible bugs and problems sooner rather then later.

I'm specifically interested in problems regarding booting from a kernel RAID device and adding existing/new drives to the RAID array ( to my understanding creating a RAID device erases all data on the partitions used for it) .

Originally posted by r2d2
Has anyone had any bad experiences with Linux software "RAID"?

I've been experimenting lately with Promise ATA-RAID (the "driver based crap) and 3ware Escalade ATA-RAID (hardware based) controllers, but the experiences have not been anything spectacular.
Promise does not deliver at all, in the sense of reliability and 3ware Escalade somehow does not perform well in speed tests, especially on the FreeBSD 4.X platform.

So as one of the alternatives we've been starting to look at Linux kernel based RAID.
My tests so far have shown no problems at all, which makes a paranoid person like me a little nervous :) . I'd like to deal with possible bugs and problems sooner rather then later.

I'm specifically interested in problems regarding booting from a kernel RAID device and adding existing/new drives to the RAID array ( to my understanding creating a RAID device erases all data on the partitions used for it) .

Booting from RAID partitions and adding new drives to a RAID array should normally not give you any problems, given that you run a recent Linux distribution.

When adding new drives you'll ofcourse have to make sure the new drive is at least the same size as the others, but apart from that - it should be more or less problem free.

Regarding hardware RAID: I've had very good experiences with the Adaptec 2400A hardware RAID controller.

I have a tyan board (only 1 thank god) with onboard Promise raid, lets just say I connected 2 hds to the cdrom and non raid slots and did software raid :)

the company I Worked for had RAID on their systems, it was very reliable, they had 5 hard drives that were swapping.
Quite redundant

Which type of Raid, ?

A project that I have been involved in has supported software RAID on Linux since 1998, with installations in hundreds of locations.

Especially since the latest 2.2 kernels, it works great (stable) in production.

Not sure why you would get superior performance over a hardware RAID, though.

Originally posted by bitserve
Not sure why you would get superior performance over a hardware RAID, though.

Software RAID uses the main CPU to do it's calculations.
Good hardware RAID cards have a seperate CPU to do that.

Also most good hardware RAID cards have cache memory on the board, they do not transfer as much on the bus as the software RAID does, etc.

Originally posted by jks
Software RAID uses the main CPU to do it's calculations.
Good hardware RAID cards have a seperate CPU to do that.

Also most good hardware RAID cards have cache memory on the board, they do not transfer as much on the bus as the software RAID does, etc.

So how does this translate to software RAID being faster than hardware RAID?

Thanks. :)

Originally posted by bitserve


So how does this translate to software RAID being faster than hardware RAID?


It doesn't.

I've never said that.

Adaptec 2400A hardware RAID controller

I too have heard good things about those Adaptec cards but have no personal experience - I have found the promise controller to be problematic in installation so won't use them, I also know people who do use them and don't recommend them for linux - depending upon your useage - software raid is a good solution and you don't have any hardware issues to deal with - It's not that hard to set up and works well. :D

Originally posted by MaB
I have a tyan board (only 1 thank god) with onboard Promise raid, lets just say I connected 2 hds to the cdrom and non raid slots and did software raid :)

er...I just bought a Tyan Tiger 200T with on board Promise raid. Did I do a bad thing?

Yeah you did.

Disable the onboard raid by the jumper and youre A OK.

I have a server with 7.2 with promise raid. I am quite stuck with the Kernel. Having a whooping time just trying to upgrade it and work the with FT drivers.

I have 4 40 GB HDs Running 0+1 mode and it is fine. (running raid 0 mode will be quite pointless) The servers a dualie so I am relatively patient with the loads. If you only have one processor, I would really recommend that you do not use the onboard Raid.

Originally posted by jks
It doesn't.

I've never said that.

You're confusing me. :eek:

Originally posted by Cephren
Yeah you did.

Disable the onboard raid by the jumper and youre A OK.
I bought this board specifically because it had the onboard raid, meaning I could have hardware raid without sacrificing the pci slot.

I have a server with 7.2 with promise raid. I am quite stuck with the Kernel. Having a whooping time just trying to upgrade it and work the with FT drivers.
So, if I understand you, the Promise raid messes with the kernel?

I have 4 40 GB HDs Running 0+1 mode and it is fine. (running raid 0 mode will be quite pointless) The servers a dualie so I am relatively patient with the loads. If you only have one processor, I would really recommend that you do not use the onboard Raid.
This is my first attempt at collocating and so, I was getting an entry level system (who knows, I may hate collocating). As a result, I have started off with just 1 processor.

Your news is disappointing, but I'm glad I heard it before I actually assembled the system.

Thanks for your words of wisdom.