Chipset Serial ATA RAID Performance Exposed

TheRaindog writes "Serial ATA RAID has become a common check-box feature for new motherboards, but The Tech Report's chipset Serial ATA and RAID comparison reveals that the performance of Intel, NVIDIA, SiS, and VIA's SATA RAID implementations can be anything but common. There are distinct and sometimes alarming performance differences between each chipset's Serial ATA and RAID implementations. It's also interesting to see performance scale from single-drive configurations to multi-disk arrays, which don't offer as much of a performance gain in day-to-day applications as one might expect."

Comments

Best Upgrade

[swordboy]

I think that the hard drive is the most overlooked upgrade for a "power user". If at all possible, go out and pick up a 15krpm Ultra SCSI hard drive and controller for the boot partition. Use that slow ATA crap for storage of non-performance type stuff.

18 or 36 gig drives aren't exactly too expensive given the performance that they offer.

Re:Best Upgrade

[Lead Butthead]

Good deal, ONLY if the manufacturors are being honest with drive spec. Several coworkers that used to work for Quantum have indicate that the actual drive mechanism used in SCSI and ATA drives frequently shares common mechanical parts (platters, spindle motors, etc.) Their differences are ENTIRELY artifical. SCSI drive spec at times looked "better" in part because of the firmware difference and cheating on SPEC; for instance seek time for SCSI drive are computed differently to create the illusion that somehow SCSI drives seek faster...

Re:Best Upgrade

[tuxlove]

How does RAID 1 help loading times? RAID 1 is all about mirroring.

Mirroring generally improves performance, which most users and most inexperienced engineers don't realize. Because you have the exact same data on at least two different spindles, you can transfer data with twice the concurrency, and at times approaching twice as fast. When reading a large file, for instance, if each disk can transfer, say, 10 MB/second and the file is 20 MB in size, the file can be loaded in one second with mirroring and two seconds without.

In addition, concurrency allows you to load two different files simultaneously on different disks. Not only do you get faster transfer times, you don't suffer from disk head seeks back and forth as you read the files. This can actually improve "load time" by much more than twice.

Since most filesystem operations are reads, the concurrency gained by mirroring usually helps immensely. However, writes do not suffer significantly either. When you write to a file on a mirrored filesystem, it obviously must be written out to both sides of the mirror. But, it doesn't take twice as long, as one might immediately think. Data can be written simultaneously to both drives, at a cost which is only marginally slower than writing to a single disk (assuming they are attached to different disk controllers/buses, as best practices dictate).

All-around, mirroring is very good for performance.

Question about striped/mirrored raid

[biscuit67]

Does the raid driver typically allow two independent seeks on the seperate drives with mirroring enabled? I would expect this to significantly improve things like boot times as most of the time is spent seeking for new data. I would have expected a 50% drop in seek. If they don't do independent seeks, why the hell not?

Re:Question about striped/mirrored raid

[Tranzig]

Don't forget that those RAID controllers are just toys for the kiddies. Industrial grade RAID controllers have on board processor and memory, and they do optimize the read access for RAID 1 arrays. Though they don't halve seek time on two disk arrays, they still provide noticeable speedup for reading.

Built-in RAID chipset performance has always...

[Dagny Taggert]

..been a sore spot with me. Most users do a RAID 0 setup so their cool rig is hottie fast. Truth is, I can't see much real world performance difference. For my money, a large SATA drive and an external FireWire for backups is the way to go. Simple setup, no worries about drive failure and losing data, and still fast enough for UT2004.

Re:Too Many Checkbox feature

[Anonymous Coward]

Remember the days when IDE/SCSI was all you needed.

Yeah, when all you had to worry about was MFM or RLL? ST506, IDE, E-IDE, Western Digital IDE, ATA, ATA-2, ATA-3, ATA-4, ATA-5, ATA-6, SCSI, SCSI-2, SCSI-3, Wide SCSI, Fast SCSI, Fast SCSI-2, UltraWide SCSI, Ultra SCSI-160? Connectors were just as simple; 40pin, 44pin or 80pin? 25pin D conector for external SCSI, male or female? How about a dense 50 pin D connector, or wait, maybe 64pin? 50 or 64 pin cable for internal drives; your choice.

Don't forget to setup your SCSI bus and wave that chicken. Does your SCSI controller boot from SCSI ID 0 or 7? Maybe 6 or 4? Did you set your master and slave jumpers on those IDE devices properly? Your IDE performance sucks; you didn't put a PIO device as a slave on the same channel as your screaming-fast UDMA166 120Gb hard drive now did you? By the way, does your BIOS support 48bit LBA for that drive? Got SCSI terminators. Need a terminator block or is it an internal jumper perhaps?

Oh boy, things were so much simplier back then..

Re:Too Many Checkbox feature

[Anonymous Coward]

Got SCSI terminators. Need a terminator block or is it an internal jumper perhaps?

Dear god I'm having sysadmin flashbacks now. Gonna be thinking of sendmail.cf all day...

Bastard.

RAID vs. single drive performance

[fugu]

storage review did a writeup a while ago comparing RAID 0 performace to that of a single drive. more often that not you're better off getting a single, faster drive if you're looking for desktop performance.

Wrong

[sczimme]

I normally don't respond to ACs, but this one is just incorrect.

Yes, RAID {1|5|10} are generally used for their redundancy purposes, but RAID 0 is used because it offers improved I/O performance. It is certainly not used for redundancy because - guess what - it doesn't offer any on its own*. Go read this before you provide more misinformation.

* it can be used in combination with other levels - e.g. RAID 0+1 - to provide performance and redundancy.

Surprise, surprise, surprise

[Anonymous Coward]

Why do folks act shocked when commodity hardware behaves like commodity hardware?

Why should computer hardware be exempt from the "You get what you pay for?" dictum which dominates other markets.

And when you make millions and millions of any one thing, a "couple of pennies a chipset" adds up. Once again, that's what you get when you buy a commodity.

RAID Perfomance

[Berylium]

For the past 3 years I've had a RAID array set up on my home computer. It is a RAID 5 array with four 18GB Seagate X15 hard drives on an AcceleRAID 170 PCI card. I'm on the computer several hours a day during which time I play various video games, program in visual studio, and transfer a bunch of MP3 sized files and very large video files (~2GB). From my experience, the RAID 5 is definitely faster in some tasks than a high-performance ATA drive (like game loads) but for the types of activities I'm doing the expense of the SCSI drives and the noise they generate is more costly to me than the (perceived) slight speed disadvantage of a single disk serial ATA drive.

Don't get me wrong, the RAID 5 array is sweet and certainly amps up geek appeal, but I don't have enough friends who know what the hell a RAID array is to really impressive them.

-Berylium

Driver software is probably key

[Anonymous Coward]

Since every SATA raid controller (bar the i960 based one from adaptec) is done using software, I reckon that what is actually benchmarked here is how optimum the drivers are, not the hardware performance. Besides (I'm guessing, as I only read the conclusions page) that each of these interfaces is connected off of a crummy 32 bit 33MHz PCI interface... That's the real killer right there.

I have a Dell PowerEdge in the back room with 2 15k scsi drives running linux and raid 0 - with hdparm -t this thing gets 125-128 mb/sec! The HD interface on that machine is definitely hung off of a PCI-E interface or something better; as the maximum theoretical transfer rate of PCI is about 33*32 million bits per second or 132 megabytes per second.

What would be really nice is if the filesystem was put on the i960 based adaptec card...

RAID 0,1,5

[mr_rizla]

Raid 0 = striped disks for improved performance. No redundancy. In fact, increasing your chances of losing data because if one goes down, no chance of data recovery. (total storage = total of disks)

Raid 1 = Mirrored disks, writing same data to all disks so if one fails you simply replace it and no loss of data. (Total storage = 1/2 of disks)

Raid 5 = Redundant striped disks. One of the disks is used to store a XOR bit, so that basically any one of the disks can go down and once it is replaced the RAID system will rebuild the data on to that disk. (Total storage = total storage of (all disks minus one))

In RAID 1 and RAID 5, which is used in business servers, you really need hotswappable drives so any drives going kaka will not impact the server in any way, just replace the hard drive under warranty without even rebooting the server and the RAID system will rebuild the drive.

RAID 5 is most effective in a business situation, offering a good compromise of speed, capacity and redundancy.

Re:RAID 0,1,5

[bobv-pillars-net]

RAID 5 is most effective in a business situation, offering a good compromise of speed, capacity and redundancy.

Nope. In a real business situation, i.e. data-warehousing or ISP hosting environment, nobody trusts RAID 5. It's slow and fragile. Instead, everybody I know goes with RAID 10 (striped mirrors). Here's a typical 8-drive configuration:

Stripe:

1. Disk 1 mirrored with Disk 2
2. Disk 3 mirrored with Disk 4
3. Disk 5 mirrored with Disk 6
4. Disk 7 mirrored with Disk 8

Total storage equals the same as a 4-drive RAID-0 system. Performance should be slightly better, on a high-end dedicated controller, as the mirrors should be able to seek to different files independently for concurrent read requests (thus lowering latency), while the stripes should be able to operate simultaneously for large-block i/o (thus raising the streaming i/o rate).

Reliability is better than Raid-5, for two reasons:

1. When a drive fails and is replaced, only that particular stripe is rebuilt. That means that until the rebuild is done, one drive will be doing streaming-reads, and the other will be doing streaming writes. None of the other drives are affected. Contrast this with Raid-5, where one drive is doing block-writes and all the others are doing block-reads, interspersed with CPU checksum calculations, until the entire drive array is rebuilt. The result is that RAID-10 has much shorter disaster recovery times.
2. In a RAID-10 system, up to half the drives can fail simultaneously without data loss, as long as one drive in each stripe remains functional. In a RAID-5 system, the loss of two drives guarantees loss of all your data.

3Ware s-ata hardware RAID

[Axello]

I've been using a couple of 3Ware hardware RAID cards in my FreeBSD servers. More expensive than the onboard crap, but Very Nice. Full hardware RAID 0,1,10,5,50, remote control, hot swap, hot spare, email notification on failure, the works.
You can configure your RAID remotely while your server is running. (But always be careful with your boot disc ;-) Or you can install your OS while the RAID is building in the background. Works with Linux & Windows as well, unfortunately not with MacOS X.
But for MacOS X (& linux) geeks, the XRaid RuleZ!