Putting the Redundancy in RAID: RAID-1

The next type of RAID that we'll talk about is RAID-1, otherwise known as mirroring. We won't be benchmarking RAID-1 here because, for the most part, there's no performance increase or decrease. As the title of this page implies, RAID-1 is done for redundancy.

Writing to a two-drive RAID-1 array

Unlike RAID-0, there is no preprocessing done on the data before it is sent to the hard drives. Instead, with RAID-1, a duplicate of everything written to drive 0 is written to its mirror drive. The benefit of RAID-1 is that if one drive fails, you have a perfectly working backup that can take over until you have replaced the failed drive. You have effectively doubled a single hard drive's mean time between failure by using two in a RAID-1 array. You'll notice that this is the exact opposite of RAID-0, but the downside to RAID-1 is that you spend twice as much on hard drives without getting any additional capacity or performance, just reliability.

Doubling Theoretical Performance: RAID-0 The Test
Comments Locked


View All Comments

  • bhvm - Tuesday, June 22, 2010 - link

    Agreed cent percent.

    Whereas our processors are zooming in Ghz and Rams in GBs... Our old humble HDDs are still around 60MB/.s

    A properly setup RAID (with dedicated controller) will give close to 90% performance boost. I run Software RAID 0 on my laptop (its a monster laptop with 2 x 7200 RPM seagate momentus) for My database... Its just not about the Raw speed and numbers... the machine 'feels' damm so fast. Also, despite being software RAID, Single drive gives 45MB/s.... Whereas RAID 0 partition gives easily 85 MB/s/.

    Long live the RAID!
  • Ambress - Wednesday, November 10, 2004 - link

    While this article on RAID was quite informative, I would be very interested in seeing what the measured peformance differences are for an application such as Photoshop, where a secondary hard drive assigned as a scratch disk is recommened for optimum performance. Perhaps one problem here is finding some reliable Photoshop benchmarking tool, but surely one exists. Even without that, just performing a repeatable action that exercises a series of steps that are certain to force scratch disk usage could demonstrate what RAID 0 advantages exist, when used as the scratch disk. Such a test would likely require the manipulation also of a rather large image file...perhaps 100MB or more. I suspect other applications that work with large data files, such as video editing applications, would also benefit noticeably from a RAID 0 array. If this doesn't prove to be the case, then my plans for my next PC could be simplified and costs reduced. I've anticipated building a system with a RAID 0 system drive and a RAID 0 data drive, although I'm now thinking that RAID 0 for a system drive may be overkill.
  • DatabaseMX - Tuesday, October 19, 2004 - link

    At the beginning of the article:

    "Unfortunately, if you lose any one of the drives in the array, all of your data is lost and isn't recoverable."

    If you lose your drive in a single drive system, all of your data is lost and isn't recoverable, thus, the above statement has no special meaning. However, in both cases, if you have backed up your drives, then you can recover. Also, I fail to see how two drives in a RAID 0 will halve the MTBF.

    This review is hardly based on any scientific approach - one controller / motherboard combination and one brand of hard drive. Get real. And to not delve into WHY there was only minimal performance increase further dilutes the results of this review/test.

    #64 pretty much spells it all out - nice job.

    #87 (et.al) ... It doesn't matter if it doubles, triples or 1000 times it ... just like with ONE drive ... you are hosed if you don't have a full system backup! The primary concept of RAID 0 is to get more performance, not to worry about drive failure. If you are worried about drive failure, then use RAID 1 or some other RAID level which deals with redundancy.

    Backup is the key here. And I can attest that Acronis True Image (www.acronis.com) is one brilliant piece of backup software. I have used it in multiple scenarios, including restoring an image file on to a brand new, un-partitioned, un-formatted hard drive (both IDE and SCSI), then booting up with the new drive - restored 100 %. And the good news .... it supports (some) SATA RAID configurations - and the new Promise FastTrak TX2200 controller (according to Acronis tech support).

    So, the issue is NOT about the so-called dangers of a RAID 0 array and drive failure and statistics and probability, but instead >> performance. It's time to create some new benchmarks that focus specifically on testing RAID configurations, ie back to the future, instead of all the sorry old benchmarks mentioned above.

    I will be interesting to see how new Promise FastTrak TX2200 SATAII controller connected to a pair of the new Maxtor SATA DiamondMax 10 300GB, 16MB in a RAID 0 configuration fairs out in tests. In fact, it would be interesting to see how the Promise FastTrak TX4200 with 4 Maxtor drives in a RAID 10 configuration works out. Best if both worlds - performance and redundancy? Since both the new Promise controller and Maxtor drives support NCQ and SATA TCQ ... one would think this should make a dent in RAID 0 (and RAID 10, etc) performance. I'm about to find out ... as soon as the TX4200 arrives at my door step.

  • MplsBob - Wednesday, October 13, 2004 - link

    I surely do wish that this testing of RAID 0 had included the unique cards from Netcell. Their SyncRaid line looks as though it might be promising, but in the end are their results in "real world" testing sufficently good to make it worthwhile.

    How about it AnandTech, could you expose one of these SyncRaid cards to the same testing you had in this article?
  • kmmatney - Monday, September 13, 2004 - link

    I would haveliked to see the differences using RAID with slower hard drives. Not everybody has a Raptor. Does RAID have a greater impact if the hard drives are slower to begin with?
  • mbor - Tuesday, August 24, 2004 - link

    btw, a striping array of 2 raptors shouldn't be called RAID, but NAED:
    Non-redundant Array of Expensive Disks ;)
  • mbor - Monday, August 23, 2004 - link

    I find the conclusions in the article surprising. When I have bought a second drive and configured it in a RAID 0 array, the performance increase could be clearly seen. I was so impressed that the first thing I'm looking for in the next mobo I plan to buy is a good RAID controller with 4 drive RAID 0 capability.
    Perhaps the tests simply don't show it, but in reality, at least in my case, the performance did increase noticeably.
    You can even see it in Windows Explorer. Opening a directory with a couple hundred files inside is faster than with a single drive. The same applies to other apps that work on large ammounts of data.
  • Pumpkinierre - Friday, July 9, 2004 - link

    Nicely put mdrohn, I still dont regard backup as superfluous. Its really terms like: extra redundancy or built-in redundancy etc. that grate with me. The term seems to be used for things that mean error protection or failure proofing. In Raid1 the second disc is superfluous as far as extra storage goes, but it can be used for simultaneous reads or even striped reads which improve speed as well as backup - hardly supefluous. My usage of the word has been as 'not needed' more akin to obsolescence than anything else. But apparently the term is widely used in the electronics industry. So perhaps another example of English being subroutined (or bastardised).

    At least we made it to 3figures in the posts and page 6.
  • mdrohn - Friday, July 9, 2004 - link

    Well, my Aussie friend, since we're splitting linguistic hairs, I maintain that the primary meaning of 'redundancy' (from the latin 'redundare' meaning 'to overflow'), both linguistically and electronically, is in its sense of 'superfluity or excess'. The sense of 'uselessness' is a secondary meaning which has evolved from that primary one. Every dictionary I have checked lists the superfluous sense above the useless one, which is an indicator of semantic primacy.

    But I suspect that this discussion has become somewhat redundant, since we both seem to be making the same points over and over again ;)
  • masher - Friday, July 9, 2004 - link

    Interesting read on storagereview, Timw. It proves what I suspected-- that beyond 3 disks, performance for large Raid 0 arrays actually declines. It also demonstrates that Raid 0 using slower disks isn't appreciably better than with pricey Raptors.

    Also interesting...for single-user operation, command tagging and queuing tends to decrease performance.

    The past postings to this thread demonstrate why some people believed in a flat earth up to the 19th century, and some today think the Apollo moonlanding was staged by Hollywood. People cling to illusions, despite reality.

    To use technical terms, Desktop Raid-0 sucks. Get over it.

Log in

Don't have an account? Sign up now