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

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.

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.

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.

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!