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How GNU/Linux and Serial ATA RAID teamed up to save money
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CommentsWhile the product was in development, RAIDCore was an independent company working with Mailroute as it developed a GNU/Linux product. When chipmaker Broadcom acquired RAIDCore earlier this year, there were some concerns that Linux support would get lost in the shuffle. Did one privately held company have enough sway to get Linux drivers and software support from Broadcom? "I'd like to think so," Mailroute CEO Thomas Johnson told NewsForge.
On Monday, Broadcom officially announced the release of its new BC4852 RAID controller, but Mailroute has been beta testing the product for some time. This product reputedly offers the same high performance and large number of disks as competing SATA RAID products from 3ware and others at a substantially lower price. But, just as GNU/Linux is overtaking proprietary Unix installations, SATA RAID is beginning to overtake SCSI RAID in production environments.
Johnson and his engineers originally tested the RAIDCore card on Windows-based machines, since the hardware didn't have drivers for other operating systems. But since they didn't use Windows in their production environment, the product was useless to them. So Johnson called RAIDCore and told them that he liked the hardware but needed software and drivers that would work with GNU/Linux -- specifically Red Hat 9. RAIDCore engineers began development of Linux drivers and software, and Broadcom allowed them to continue their work.
"We've got IBM xSeries 235 and 335 systems, one's a tower and one's a 1U rackmount box. We asked IBM if they could add a hot-swappable SATA backplane, and they couldn't help us. So we ripped out their SCSI backplane and put our SATA drives in," Johnson said. The small 1U rackmount form factor also requires half-height peripheral cards; not only is the Broadcom RAIDCore BC4852 a half-height card, but it comes with rear faceplates for both half and full-height chassis.
| Why SATA RAID? |
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Serial ATA is the connection standard of the future for hard drives. Standards come and go as technology advances, but for the next few years, if you want a quality, inexpensive hard drive, it's going to have to be SATA. The only real difference between SATA and SCSI or parallel ATA is the electronics and the connection standards; the mechanical components of the drives are the same. Traditionally, SCSI has been the standard for mission-critical systems in production environments; it offers outstanding performance and high reliability at a premium cost. Usually you'll find production servers running RAID to enhance system speed, reliability, and storage space. There are many different RAID modes, but RAID-5, which combines three or more disks to increase storage space while simultaneously offering redundant data protection, is the most popular. The RAID controller takes the drives connected to it and manipulates them to your preference. If you have a number of identical hard drives, you can consolidate their space and efficiency by putting them into an array via a RAID BIOS, which is much like your computer's BIOS except it only affects the RAID controller. When the system gets past its power-on self test, the RAID is seen by the system as one disk, assuming you have the proper driver for your operating system. Some controllers, like the ones built into Intel motherboards, will allow you to simply connect a drive and use it standalone without having to go through the RAID BIOS. |
The BC4852 requires Broadcom's proprietary software to take advantage of its most interesting features, and the Linux drivers are also closed-source -- for the time being, at least. A Broadcom representative told NewsForge on Monday that the drivers would be open sourced in 1Q 2005. That's good news for their customers -- especially Mailroute.
"I'd really like to see the Broadcom driver in the Linux kernel," Johnson said. "When I can get the driver through the default installation, the product gets a bigger vote of confidence from me than when we have to get drivers from a third party."
"We had such a large call for Linux support that we decided to engineer Linux drivers," Jeff Huber, a Broadcom representative told us last week. The Broadcom drivers were not ported or adapted; they were written specifically for GNU/Linux. According to Huber, only the Windows edition of the controller software has a graphical user interface; the GNU/Linux edition is controlled through the command line interface.
Currently the RAIDCore BC4852 drivers and software only support Red Hat Linux 9, Red Hat Enterprise Linux 3, and Fedora Core 1.
Broadcom sent us a controller to review, but the driver installation procedure involved using a diskette, which this reviewer has not had or needed in several years. Broadcom rushed to get us an ISO so that we could use a CD instead, but as of Monday afternoon we still couldn't get it to work properly on Red Hat 9 or Red Hat Desktop. Broadcom is, however, working to resolve the issues and hopes to offer tested and qualified ISO images as an alternative to diskettes.
Jem Matzan is the author of three books, a freelance journalist and the editor-in-chief of The Jem Report.
Comments
on How GNU/Linux and Serial ATA RAID teamed up to save moneyNote: Comments are owned by the poster. We are not responsible for their content.
-Jem
Well, then I'll consider Broadcom SATA in a few months. Until then, onboard SATA with software RAID and 3WARE (depending on platform requirements) are meeting open source requirements just fine.
I'm a systems admin, and as an interesting conincidence we had a discussion today of purchasing an ATA-RAID system for our aging, but working NFS filesystem.
So obviously, it was with some interest I read the article. It was disappointing to find that the drivers are closed source.
Now, it's not really out of free-software zealotry , but rather the fact that in my experience, third-party kernel modules (open-source or not) are more hassle. Apart from the aforementioned NFS system, we also have an system running on AFS. Matching OpenAFS binaries to the kernel version is simply a lot of work. And we really don't have the time to do a separate compile and install on each machine.
So.. If they GPL their drivers so that they can be integrated with the kernel, then we will seriously consider using their hardware. But I can't see us migrating otherwise, risk creating the headache of not being able to upgrade without breaking the driver.
0, 1, 1N, 10, 5, 50, 10N, JBOD
It has eight SATA ports and can be "Stacked" with other RAIDCore SATA controllers to create gigantic arrays.
It's PCI-X, and you don't want to have an array larger than 6 disks unless you're using it on a 100mhz or 133mhz PCI-X bus.
Performance reviews are coming in the future, but maybe not on NewsForge -- more than likely they'll go on my site.
-Jem
What would you prefer? RedHat clearly has the largest installed base and probably the most stable distro out there. Even their Fedora project seems more stable than Suse - the next vendor I would consider. All the others are just too wild to consider. If it will work under RedHat, it should work under some other distro's, including Suse. Fortunately the binaries seem to work well together.
It is stupid and shortsighted to only provide Red Hat binaries- what about Debian, Slackware, and other users? That's just as stupid as saying "oh, only Windows users matter." I completely do not understand why hardware manufacturers are so idiotic about drivers. Like duh, don't they want to sell product?
3ware stuff works GREAT! I have 2 multi-terabyte boxes now. More on the way. The first 3ware box I built I was a 4 channel controller, 4 250 gig drives, would rebuild a 750 gig array in under
2 hours.
I was sold!
good stuff.
Bye bye Broadcom!
Remember the TCQ you enable for your SCSI drives ? This means that the commands sent to the disk will be executed in an order decided by the drive so that the mechanical movements are optimized (ok, with some limitations) And mechanical movement is most of what a disk does. In a multithreded environment (linux is) this matters a lot under concurrent accesses.
Most of the SATA disks are still normal ATA with an adaptor. Which perform badly in multithreading environments as they perform the commands one by one.
Wonder why nobody talks about that. Or maybe I'm wrong. Or maybe PR people use only windows workstations (and Doom doesn' do to much parallel disk I/O anyway)
Yes, more reliable, but at well under a buck a gig, per drive, who cares?
I know I certainly don't. Not at all.
Before you knock a 3ware array, you ought to try one sometime.
Those who care about reliability over price do. Not joe kid at the parent basement, obviously.
As far as reliability is concerned, most drives that are going to die are going to die right away (DOA or soon after). And this is why you have a redundant array -- 5 or 50 -- so that you can lose a drive and not lose the data. In the kind of arrays I'm talking about in the article, the negligible difference in lifetime reliability of SCSI and SATA drives is an insignificant factor.
SATA 7200RPM drives can also hold a hell of a lot more data than a SCSI 10k or 15kRPM drive which will cost more than twice as much. So you could build an SATA array of the same size as your SCSI array and take the money you saved and buy a few extra disks to provide better data protection.
-Jem
tagged queueing, and thsi gives just about the
same TCQ/scatter-gather performance as SCSI
host adapters.
else then i would like them to send ME their
scsi discs. i will take good care of them.<nobr> <wbr></nobr>:)
What about the reliability? If a RAID disk goes down it costs a lot of time to rebuild it. You have to put in an exact similar version.
(Partly addressed to this person above who's convinced SATA is gonna be 'the bomb'. Current high-end industry standard is SCSI-3. How about backward compatibility?)
In terms of reliability, you gets what you pays for. But SATA is brand new. Wait a few years and you see a lot of high end drive options available that still beat out SCSI options in terms of price. And no, in order to do SATA RAID, the drives do NOT have to be identical. SATA simply maps in compliance with the smaller drive.
Compatability is a problem and so are other issues such as write ahead cache, but these WILL be addressed and SATA will become ubiquitous just like USB. And by the way, there IS a new SCSI standard that implements SCSI with all the same features provided by SATA on the ATA side. I would not be surprised if that were to become the new high end standard and it will likely be backward compatible with previous SCSI hardware.
Bet the RAIDcore *still* missing hardware XOR
Posted by: Anonymous Coward on September 24, 2004 02:44 AMI'm a fan of SATA RAID, but I still don't think it's there yet<nobr> <wbr></nobr>:-(
<TT>[jackson:stock]:(~)$ dfyes thats 640 Gbytes mounted on my Tyan Thunder K8W station.... the cost of that SATA storage ? Well go shop for yourself, but its around $500,= which is a stunning $0.75 cents per GigaByte.
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda2 114390056 12050620 96528728 12%<nobr> <wbr></nobr>/
/dev/sdb2 114390056 18683408 89895940 18%<nobr> <wbr></nobr>/mnt/data
/dev/sdc1 192292124 10422008 172102196 6%<nobr> <wbr></nobr>/mnt/dvdrip1
/dev/sdd1 192292124 20838512 161685692 12%<nobr> <wbr></nobr>/mnt/dvdrip2</TT>
Performance ?<nobr> <wbr></nobr>:
<TT>[jackson:root]:(/mnt/dvdrip1)# time cp mdk100-amd64.iso<nobr> <wbr></nobr>/mnt/dvdrip2so thats roughly 3gigs in 1 minute and 15 secs. Recalculates to 40 Mbytes/sec data copy
0.14user 18.71system 1:14.65elapsed 25%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+168minor)pagefaults 0swaps
[jackson:root]:(/mnt/dvdrip1)# ll mdk100-amd64.iso
-rw-r--r-- 1 root root 3006515200 Sep 13 19:08 mdk100-amd64.iso</TT>
Hey Mr. SATA i'm your man<nobr> <wbr></nobr>:)
Robert
http://www.digitalson.com/raidcore.htm
that should tell you everything you need to know about this card AND company!
broadcom? let me guess...
Posted by: Anonymous Coward on September 21, 2004 10:10 PM#