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flatmodel
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PostPosted: Fri Feb 07, 2020 8:56 pm    Post subject: Dell Hardware RAID controller problems Reply with quote

Hi Guys,

Well, I've fallen down the hole of the Dell S300 RAID controller not being supported under Linux, at least posts from 2013 and now personal experience would seem to suggest that. I had hoped that after some seven years a driver might be available, but it would seem not.

Can anyone recommend a good hardware RAID controller that will work under Linux? There seems to be a good selection available on eBay for not much money, but I don't want to waste time on controllers that only work on Windows platforms.

Many thanks in advance,

Richard.
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mike155
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PostPosted: Fri Feb 07, 2020 9:21 pm    Post subject: Reply with quote

Do you want a hardware RAID controller or a software RAID controller?

As far as I can see, the Dell S300 RAID controller is a software RAID controller.

If you care about your data, don't use software RAID controllers like the Dell S300. Either use a hardware RAID controller with battery backup or use the RAID features provided by the Linux kernel and associated userspace programs. But don't use the RAID features of the Dell S300 RAID controller.

If the Dell S300 RAID controller provides a working pass-through mode which allows to use the drives as normal drives, you could use that mode. Add the RAID features provided by the LINUX kernel and you're done.
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flatmodel
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PostPosted: Fri Feb 07, 2020 9:35 pm    Post subject: Reply with quote

mike155 wrote:
Do you want a hardware RAID controller or a software RAID controller?

As far as I can see, the Dell S300 RAID controller is a software RAID controller.

If you care about your data, don't use software RAID controllers like the Dell S300. Either use a hardware RAID controller with battery backup or use the RAID features provided by the Linux kernel and associated userspace programs. But don't use the RAID features of the Dell S300 RAID controller.

If the Dell S300 RAID controller provides a working pass-through mode which allows to use the drives as normal drives, you could use that mode. Add the RAID features provided by the LINUX kernel and you're done.


The S300 is a hardware RAID controller, one creates a virtual disk at the BIOS level, and then the virtual disk becomes, say, /dev/sda once the operating system is up. However, in the absence of a driver to support this, I'm stuffed unless I use Windows, which is just not an option! You're right in that I'd like to have a hardware RAID controller with the backup battery and so forth; but what to opt for is the question?

There is no pass through mode, unfortunately, so the S300 is useless in the Linux setting (I tried this before I posted the question). I haven't ruled out the option of having the kernel do the RAID for me, but I still need a suitable controller in any event.
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PostPosted: Fri Feb 07, 2020 9:42 pm    Post subject: Reply with quote

The S300 is a fakeraid controller. It is not a hardware RAID controller.
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PostPosted: Fri Feb 07, 2020 10:09 pm    Post subject: Reply with quote

Jaglover wrote:
The S300 is a fakeraid controller. It is not a hardware RAID controller.


Well, OK, in any event it's useless under Linux, so it's a question of where to go from here.

I'm desperately clinging onto my old SCSI server until I have a workable solution for this new SATA/SAS disk subsystem on a T310 server.

A quick look on eBay would suggest that I can buy a reasonably inexpensive solution (with the extra complication of needing a suitable cable to connect the disk backplane); but I really would appreciate any guidance at this point.
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PostPosted: Fri Feb 07, 2020 10:11 pm    Post subject: Reply with quote

https://serverfault.com/questions/341125/installing-linux-on-dell-poweredge-t-110-perc-s300

^^ There is a workaround, if it fails you got to keep the pieces ...
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PostPosted: Fri Feb 07, 2020 10:17 pm    Post subject: Reply with quote

flatmodel,

Dell say that the S300 is a software raid controller.
They really mean its fakeraid

Fakeraid is the worst possible raid solution. The only excuse for using fakeraid is that Windows and Linux both need to work with the raid set.
If you have fakeraid, disable it and use Linux kernel raid. Its both faster and safer.

To poke at fakeraid in linux you need to
Code:
emerge sys-fs/dmraid

That may see your fakeraid raid set. Its been version 1.0.0_rc16-r4 for many years now.
Putting root on fakeraid can be done but it will make your head hurt ... even if dmraid works for you.

If you don't have enough on board SATA ports, fit a SATA expansion card that has enough PCIe bandwidth for the drives you will attach.
A single lane PCIe card for 8 SATA3 drives is a very bad idea.
One PCIe ver 2 lane is 5Gbit/sec. One SATA3 rotating rust drive is 6Gbit/sec max. (its a lot less sustained.)

This Dell page says
Dell wrote:
S300 supports pass-through (non-RAID), RAID 0, RAID 1, RAID 10 and RAID 5

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flatmodel
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PostPosted: Fri Feb 07, 2020 10:24 pm    Post subject: Reply with quote

Jaglover wrote:
https://serverfault.com/questions/341125/installing-linux-on-dell-poweredge-t-110-perc-s300

^^ There is a workaround, if it fails you got to keep the pieces ...


:lol: I wouldn't even know where to start! :lol:

Seriously though, I don't mind spending a bit of money to buy a decent controller that I'm confident will work. I'm already resigned to the S300 being useless, so I'm not going to waste much more time trying to force it to work by wrangling with firmware.
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PostPosted: Fri Feb 07, 2020 10:42 pm    Post subject: Reply with quote

flatmodel,

The Dell webside says that the S300 has a passthrogh mode.

Before you spend serious money on a couple of real hardware RAID controllers what raid level do you want, across how many drives and what is your workload?
You need a spare as a controller failure will make the drives unreadable, except on an identical controller.
Or you restore on new hardware from your most recent validated backup.

With Linux software raid, you move the drives to another system.
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PostPosted: Fri Feb 07, 2020 10:53 pm    Post subject: Reply with quote

NeddySeagoon wrote:


Fakeraid is the worst possible raid solution.



I'm resigned to scrapping the S300 card, it's a question now of what to replace it with? I only want RAID5 with four 500GB drives, and performance is a secondary consideration compared to reliability/robustness. I have been very grateful for hot-swap capability in the past, and that's a boon that I would hate to compromise upon.

No matter what I do with the S300, lsblk just shows the loop device and the CD-ROM when I boot the minimal install disk. I haven't tried the dmraid suggestion; but I suspect that the S300 is just not worth the candle given that it's such a crappy solution anyway. A "proper" RAID card supported under Linux is what's required, it's just a question of what to get?
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PostPosted: Fri Feb 07, 2020 11:04 pm    Post subject: Reply with quote

flatmodel,

For RAID5 with four 500GB drives, test drive kernel raid.
If its not good enough, its a backup and restore to migrate to HW raid.

Apart from some very early broken SATA chipsets, all SATA can be hot swapped.
Its a non optional feature of the SATA specification.

-- edit --

There is no need to use the Gentoo minimal CD to install Gentoo. Its only a toolkit.
Use any live media you have to hand.

You will need to do
Code:
mkdir /mnt/gentoo
before you can follow the hardbook.
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NeddySeagoon

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Jaglover
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PostPosted: Fri Feb 07, 2020 11:18 pm    Post subject: Reply with quote

https://skrypuch.com/raid/

They tell Linux software RAID is good until you have 12+ drives ...
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flatmodel
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PostPosted: Fri Feb 07, 2020 11:27 pm    Post subject: Reply with quote

NeddySeagoon wrote:
flatmodel,

For RAID5 with four 500GB drives, test drive kernel raid.
If its not good enough, its a backup and restore to migrate to HW raid.

Apart from some very early broken SATA chipsets, all SATA can be hot swapped.
Its a non optional feature of the SATA specification.

-- edit --

There is no need to use the Gentoo minimal CD to install Gentoo. Its only a toolkit.
Use any live media you have to hand.

You will need to do
Code:
mkdir /mnt/gentoo
before you can follow the hardbook.


I would still like a hardware controller: in the SCSI days the controller has a beeper on board so that you can readily tell there's a problem, and the OS was blissfully ignorant of any trouble. It was just a matter of replacing the failed drive and the beeper would eventually stop when the array had automagically rebuilt in the background. That's what I'd like this time around, if at all possible. I've never had a controller failure, but I guess there's always a first time. I'm paranoid about backup, so if it all went up in flames, my losses would be just the time it takes to restore the system.
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PostPosted: Sat Feb 08, 2020 12:11 am    Post subject: Reply with quote

Quote:
I would still like a hardware controller

I've been working with DELL hardware RAID controllers like PERC H710p, H730p for a couple of years.

They have onboard non-volatile cache and a battery backup unit. The RAID controllers are very fast and they work very well under Linux. DELL uses LSI controller chips and drivers are already included in the standard vanilla Linux kernel.

I've never had any problems or data loss.
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PostPosted: Sat Feb 08, 2020 12:26 am    Post subject: Reply with quote

flatmodel,

That sounds like a very expensive beeper :)

One of my raid sets is in my garage 50m from the house. The beeper would annoy my neighbours before I heard it.
Another is maybe 1000 miles away in a data centre.

I try to catch problems while there is still some life in a soon to fail drive.
That allows me to fit a new drive and tell mdadm to replace the failing drive with the new one while both are connected to the array.
When it works, the raid set is never in degraded mode, well only for a few blocks, not the entire rebuild.

Now, I have had two drives in a raid5 set fail within 15 minutes of one another. Not total failures, read errors and getting kicked out of the array.
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flatmodel
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PostPosted: Sat Feb 08, 2020 12:50 am    Post subject: Reply with quote

NeddySeagoon wrote:
flatmodel,

That sounds like a very expensive beeper :)


Not really, I have picked-up controllers for something in the vicinity of £30 (GBP) which is pretty cheap. The cable to connect the card to the backplane is, paradoxically, about the same again. Only mildly expensive, in my view anyway. I look after a number of servers across the country, and I can tell the users what to do over the 'phone, and the beeper falling silent again is most reassuring for them and for me.

I have used mdadm with external SCSI arrays, and it worked well enough (7 drives if I remember rightly). I'd use it again in a flash in this situation if I could get the kernel to see through the S300 card to the drives themselves, but it doesn't work no matter how I configure things. I'm giving up with the S300, and I'm looking for something better.
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PostPosted: Sat Feb 08, 2020 12:52 am    Post subject: Reply with quote

mike155 wrote:
Quote:
I would still like a hardware controller

I've been working with DELL hardware RAID controllers like PERC H710p, H730p for a couple of years.

They have onboard non-volatile cache and a battery backup unit. The RAID controllers are very fast and they work very well under Linux. DELL uses LSI controller chips and drivers are already included in the standard vanilla Linux kernel.

I've never had any problems or data loss.


This is what I need! Thank you indeed, sir! I shall have a look on eBay and see what I can dig up.
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