Can any sata controller support software raid 5

[DougoMan]

As long as you are using a software solution and have the SATA ports, are you OK or does the controller need to support it?

Basically I want to set up a raid 5 array on thismotherboard, which says it only supports 1+2.

 

[taltamir]

it is more of a hybrid raid... pure software is done without anything special from the controller, by the OS itself. It can do any raid.

question... are you making it into a general system, or a fileserver? if a fileserver just use pure software raid... i recommend getting opensolaris from www.genunix.org and using zfs.

 

[Emulex]

raid-5 or raid-6 requires the use of BBWC to work decently since you hit a double read and double write penalty (per write).

for most people that is ginormous enough to spend the dough on an intro raid controller. or used cerc or something.

 

[Madwand1]

Originally posted by: DougoMan
As long as you are using a software solution and have the SATA ports, are you OK or does the controller need to support it?

The next question is which software solution? If it's a *nix based RAID 5, then yes, it'll support it just fine, provided that your controller itself is supported. For Windows OS RAID 5, then the same answer applies, but write performance will be so bad that you might as well not bother. *nix based RAID 5 can give good read/write performance if configured appropriately, but I haven't personally worked with them in a long time, so am not up on the details.

 

[Yellowbeard]

I have done it using FreeNAS and Intel ICH9R and ICH10R boards. It works great for me although I am back to a 3TB (1.5TB x 2) 0+1 setup now as opposed to RAID-5.

 

[pjkenned]

Originally posted by: DougoMan
As long as you are using a software solution and have the SATA ports, are you OK or does the controller need to support it?

Basically I want to set up a raid 5 array on thismotherboard, which says it only supports 1+2.

AMD Based Motherboard!!! Might as well just get a Perc 5/i off eBay w/ the battery back up. It does raid 5, and is an 8 port SATA/ SAS controller. The two I bought came with BBU's and cables and were $120 + single digit dollars for shipping. Work great in non-Intel chipset motherboards, and with tape mods they can work fine in Intel motherboards. While not the fastest, they can still handle over 300MB/s write and 500MB/s+ read with ease. See: Perc 5/i Raid 5 with Seagate 1.5TB 7200.11's.

 

[Emulex]

speak of the devil had a intel sata raid (oem dell boxen) drop dead. did the ole shutdown restart to find the lost drive and rebuild. will P2V the box tomorrow and call it a day. i just have zero luck with the ich9R *sigh*

 

[DougoMan]

Originally posted by: pjkenned

Originally posted by: DougoMan
As long as you are using a software solution and have the SATA ports, are you OK or does the controller need to support it?

Basically I want to set up a raid 5 array on thismotherboard, which says it only supports 1+2.

AMD Based Motherboard!!! Might as well just get a Perc 5/i off eBay w/ the battery back up. It does raid 5, and is an 8 port SATA/ SAS controller. The two I bought came with BBU's and cables and were $120 + single digit dollars for shipping. Work great in non-Intel chipset motherboards, and with tape mods they can work fine in Intel motherboards. While not the fastest, they can still handle over 300MB/s write and 500MB/s+ read with ease. See: Perc 5/i Raid 5 with Seagate 1.5TB 7200.11's.

What is your beef with AMD? I can get this motherboard w/ a 45 watt Sempron processor for $50.

I was planning on using FreeNAS. Is this going to be incompatible because it is AMD?

 

[pjkenned]

Absolutely no beef with AMD... the Perc 5/i doesn't work on Intel chipsets without disabling two pins! It is just a super low cost hardware raid solution that is going to run circles around onboard raid, and it is cheap if you already want to add extra SATA ports since it gives you 8 more ports. Cache + Battery backup + more ports + dedicated IOP333 500MHz for $120 is quite a steal... and you can use it on the AMD based board!

 

[VirtualLarry]

Originally posted by: pjkenned
Absolutely no beef with AMD... the Perc 5/i doesn't work on Intel chipsets without disabling two pins! It is just a super low cost hardware raid solution that is going to run circles around onboard raid, and it is cheap if you already want to add extra SATA ports since it gives you 8 more ports. Cache + Battery backup + more ports + dedicated IOP333 500MHz for $120 is quite a steal... and you can use it on the AMD based board!

Tell me more about this incompatibility. Is it a PCI, PCI-X, or PCI-E card? And what are these signal pins that make it incompatible with Intel chipsets? I'm really surprised, Intel is the standard for chipsets. I cannot believe someone built a card that doesn't work with them.

 

[pjkenned]

PCIe x8. It is a SMBus issue. The B5 and B6 pins just need to be electrical taped or otherwise covered by a non-conductive material and it tends to work fine. I'll take a picture of it and such and throw some more info up later this afternoon. I've tried it on P35, P45, and X58 Intel motherboards and saw the same behavior each time, with both of my Perc 5/i's. It's a pretty well known issue. Nowadays I just use Adaptec cards w/ Intel chipsets and Perc 5/i's with AMD/NVIDIA. I couldn't imagine using anything less on AMD/NVIDIA platforms.

 

[DougoMan]

Originally posted by: pjkenned
Absolutely no beef with AMD... the Perc 5/i doesn't work on Intel chipsets without disabling two pins! It is just a super low cost hardware raid solution that is going to run circles around onboard raid, and it is cheap if you already want to add extra SATA ports since it gives you 8 more ports. Cache + Battery backup + more ports + dedicated IOP333 500MHz for $120 is quite a steal... and you can use it on the AMD based board!

Heh if I get that card though I won't have a free PCIe port for gigabit ethernet..

What exactly does the battery backup save you from? Your drives will still shut down during a power failure.

I've never actually set up a RAID array before. Is it seamless to turn it on and off or do you need to keep it on 24/7?

 

[pjkenned]

A single GigE port is fine on a normal PCI bus/slot.

So with decent raid controllers data is stored in cache memory (onboard RAM). This is great because RAM = Fast, as in makes SSD's look slow in comparison. The negative is that if you lose power, you would normally lose any data stored in the onboard RAM. Let's say for example, you were copying something to the RAID array, and so a 512MB cache had 400MB of data still in it when the power went out (assuming you don't have a battery for the PC). You would lose that data. With a BBU, the RAM is still powered for days even if the rest of the system is powered down. When the machine (and therefore drives) is turned on again, the cache will dump to the drives and you won't lose data.

If you are nervous about this, or don't have a BBU for the raid card, you can turn off this cache functionality.

Normal shutdowns will see the data stored in cache dumped to drives before shut downs. Even a 512MB cache takes 1-2 seconds to write to drives so you won't notice it. Here's an example of the Perc 5/i with some 1.5TB drives in Raid 5. You'll notice that the Perc 5/i can't handle much over 300MB/s writes, but can easily do 700MB/s reads: Perc 5/i Raid 5 with Seagate 1.5TB 7200.11 drives

Hopefully that helps a bit.

 

[Nothinman]

Let's say for example, you were copying something to the RAID array, and so a 512MB cache had 400MB of data still in it when the power went out (assuming you don't have a battery for the PC). You would lose that data. With a BBU, the RAM is still powered for days even if the rest of the system is powered down. When the machine (and therefore drives) is turned on again, the cache will dump to the drives and you won't lose data.

Unless of course that 400M was just shy of the journal commit entry, because no one's dumb enough to run an unjournaled fs these days, and even after that data gets commited on power on the kernel mounts the filesystem, replays the journal and rolls back that last transaction because it never got marked complete.

I would go for a decent UPS + software RAID over a RAID controller with battery backed cache anyday.

 

[DougoMan]

Originally posted by: pjkenned
A single GigE port is fine on a normal PCI bus/slot.

So with decent raid controllers data is stored in cache memory (onboard RAM). This is great because RAM = Fast, as in makes SSD's look slow in comparison. The negative is that if you lose power, you would normally lose any data stored in the onboard RAM. Let's say for example, you were copying something to the RAID array, and so a 512MB cache had 400MB of data still in it when the power went out (assuming you don't have a battery for the PC). You would lose that data. With a BBU, the RAM is still powered for days even if the rest of the system is powered down. When the machine (and therefore drives) is turned on again, the cache will dump to the drives and you won't lose data.

If you are nervous about this, or don't have a BBU for the raid card, you can turn off this cache functionality.

Normal shutdowns will see the data stored in cache dumped to drives before shut downs. Even a 512MB cache takes 1-2 seconds to write to drives so you won't notice it. Here's an example of the Perc 5/i with some 1.5TB drives in Raid 5. You'll notice that the Perc 5/i can't handle much over 300MB/s writes, but can easily do 700MB/s reads: Perc 5/i Raid 5 with Seagate 1.5TB 7200.11 drives

Hopefully that helps a bit.

OK, I got it but I don't think it is worth it in my case.

If I used the same drives in your benchmark w/ the 700Mb reads, what kind of numbers would I get from software raid?

Also, regarding the PCI card, I think I would be limited to 300-400Mbits.

 

[pjkenned]

Originally posted by: Nothinman
I would go for a decent UPS + software RAID over a RAID controller with battery backed cache anyday.

Why not have both? I do big IBM UPS's + Raid controllers w/ BBU's. Every time a power failure happens everything just shuts off in a nice and orderly fashion.

DougoMan: No clue on SW raid as there's a lot of factors there. Maybe Google it? That PCI card review is quite old. I'd be surprised if you used something like and Intel Pro/1000 MT (I think that's the PCI one) and got only 300-400Mbps assuming all else was well.

 

[Nothinman]

Why not have both? I do big IBM UPS's + Raid controllers w/ BBU's. Every time a power failure happens everything just shuts off in a nice and orderly fashion.

Price? I would have a UPS either way so why waste money on a hardware RAID controller that won't really buy me anything. Unless I want more than 4 SATA drives my current motherboard will do just fine. And even if I wanted more I'd probably just go with a non-RAID SATA controller because I can use software RAID on all of those drives. My current CPUs can do XOR calculations at 8GB/s which is much higher than any hardware I'm willing to pay for will manage.

If I can ensure that my system shuts down gracefully during a power outage what does a battery backed cache get me? More cache is never a bad thing, but I doubt that's worth the price of the controller.

 

[Emulex]

if your kernel panics you will also have an unclean shutdown with whatever your software raid cache being uncommitted.

 

[Nothinman]

if your kernel panics you will also have an unclean shutdown with whatever your software raid cache being uncommitted.

Which is true in both cases, the filesystem cache doesn't go away just because you installed a controller with a battery backed cache.

 

[pjkenned]

Yea I'm not going to say that I use the cheapest setup. But since I'm using 4U server boxes to hold mini SATA farms it's worth it. My biggest reason for not using SW raid, even though I know it is the cheaper solution is that I've become so used to Adaptec/LSI software to manage everything that I don't want to learn something new. Dumb maybe, but it works for what I need and I'm used to it. I don't have a TON of storage, but it's 12TB currently with 5TB free all stored with raid 6 + hot spare available mirrored in a second location. Compared to a $350/hr billing rate, seems like making sure everything is accessible and decently backed-up is important.

Plus, the boxes only have dual GigE uplinks so if they can do 200-250MB/s read/writes I'm perfectly happy. There are a lot of people that have much more stringent requirements, but for a single user that uses the storage to do backups and hold files, it works fine.