RAID And You (A Guide To RAID-0/1/5/6/xx)

[Anemone]

Great job Serra, well detailed while not taking 10 years to read

Like it a lot.

[stevecs]

Hope Serra doesn't mind, figured that this may be the best place to stick a copy of a raid worksheet that I've been playing with opposed to starting a new thread or (like now) having posted older versions to other threads. Mainly for calculating out the various reliabilities of the assorted raid levels (0/1/10/100/3/30/31/4/40/41/5/50/51/6/60/61) et al. I haven't really done much in the line of performance metrics with them yet as there are a lot of variables which are system dependent.

[Brian MP5T]

Subs

[stevecs]

Ok, Kind of tied into the previous post concerning raid's (and I'll probably merge them) but ran into a problem late last night/early this morning at work and needed to come up with a fast workload analysis for some windows boxes. Threw this together which uses the output of microsoft's diskmon utility (used to be sysinternals) at: (works /w nt4, 2000, 2003, xp, 32 & 64bit (haven't tried vista but may work with that as well).

http://technet.microsoft.com/en-us/s.../bb896646.aspx

spread sheet takes the output from this utility and does the math to display what your workload is. (random/sequential/average request size & response times et al). Anyway, can be used to get an idea as to what you want to do for your storage and for raids. (ie, if have more of a random workload and a majority of writes, parity raid 3/4/5/6 shouldn't be used, look toward non parity raids et al. You can use the above spreadsheet in #post 52 to determine what raids work best with your workload).

Figured no sense in wasting it and someone may find it useful here as well.

[KoHaN69]

Amazing OP, now here is my buttload of questions!

You have three options for the location of your Page File. The first is to put it on a different partition on your primary (boot) drive. By locating your Page File in its own partition (according to Microsoft) your page file will not become fragmented. Whether that's true or not, by partitioning your hard drive with a seperate Page File partition you do get to put it at a marginally faster part of your hard drive.

1.) But doesnt a second partition start closer to the middle of the drive?
Meaning that any second partition should be slower than any first, more "outer" partition?


2.) So which of the following would be optimal configuration on one physical drive with 3 partitions C:\ D:\ E:\ (partioned in that order) ?
C:\ for system D:\ for paging E:\ for games? or D:\ for games E:\ for paging?

3.) Small file means seek time > read time?

4.) Is seek/read time on a HD's spec, the average time, or the best (most outward on platter) time?

5.) So partitioning a RAID 0 setup improves the performance?

5b.) In RAID 0, can one partition to be made into RAID while others seen as single drives?
For example:

Drive1 Partition in RAID C: , Stand-alone partition D:
Drive2 Partition in RAID C: , Stand-alone partition E:


6.) If main OS is on RAID 0, should a 2GB page-file be set to another single drive for greater performance?

7.) I have 2x Seagate 320s (ST3320620AS3) I wanna raid 0, but one is 3 AAK, and the other is 3 AAE.
Does anyone know if the firmware difference will make an impact?

8.) Portability!
My post important question is: Can a Raid setup be transplanted into a new motherboard/raid card?
For example, if I make a hardwar raid 0 with my s939 nf4 Ultra-D, and later upgrade to a P35 MSI or whatever, can I take my 2 drives in raid from current, to another raid controller?

PS: WTF happened to Hybrid Drives? a 16gb flashdrive can be gotten for ~$50, why the hell am I not seeing at least 8GB flash +320GB platter drives??!

[alfaunits]

1.) But doesnt a second partition start closer to the middle of the drive?
Meaning that any second partition should be slower than any first, more "outer" partition?

It's BS to put the page file on the same drive as the OS.
I think they are presuming the seek times within the page file territory would be better this way (middle vs. start for PF, and OS in the middle), but, don't count on it, as stated in several places.
IMO, and I prefer it this way, get enough RAM, and ditch the PF. I still saw no proof of any problems from all the gossip flowers here/there

3.) Small file means seek time > read time?

Multiple small fileS. Yep.

4.) Is seek/read time on a HD's spec, the average time, or the best (most outward on platter) time?

Anandtech's HD reviews have a great explanation of what this is and how to put it into Avg. seek times as reported by say HD Tach.
I could paraphrase it, but it's better (for you to read any recent HD review on AT.

5.) So partitioning a RAID 0 setup improves the performance?

Superficial. Not real.
For some purposes, yes, it can improve performance, but whether you use 1 or 3 partitions on a drive/RAID array, to keep the OS/apps/PF - same s***, more places to worry about!

I have to add however, that putting the NTFS's MFT in the middle seems to improve open times. (most defrag utils will place it there, instead of ~10% from the start).
So, having the above in mind, forcing the PF around the middle of the drive may also be good for some situations, and I could be wrong in my assumption that it's BS.

5b.) In RAID 0, can one partition to be made into RAID while others seen as single drives?

I think you mean something like Intel Matrix stuff?

6.) If main OS is on RAID 0, should a 2GB page-file be set to another single drive for greater performance?

Ye. Try not to put it on a mirror, though.

7.) I have 2x Seagate 320s (ST3320620AS3) I wanna raid 0, but one is 3 AAK, and the other is 3 AAE.
Does anyone know if the firmware difference will make an impact?

Not on onboard RAID. If one drive is actually faster, of course changing the other would prolly give you a boost, but nothing to worry about.

8.) Portability!
My post important question is: Can a Raid setup be transplanted into a new motherboard/raid card?

Onboard RAID is not hardware, not that it matters much for RAID0 on a desktop.
Back to your question:
Intel ICHxR controllers have compatible on-disk structure, and you can swap the RAID arrays between Intel controllers (not JMicron on Intel boards!)
Intel ICHxR is not compatible with any controller I have tested (quite a few brands).
nVidia is not fully compatible between boards, IIRC, and is definitely not compatible with Intel RAID. It is compatible with some hardware RAID controllers.

Don't ever think of moving an Areca volume - you will loose the volume guaranteed.

PS: WTF happened to Hybrid Drives? a 16gb flashdrive can be gotten for ~$50, why the hell am I not seeing at least 8GB flash +320GB platter drives??!

I think they found the use is... none.
There was one Seagate hybrid drive for notebooks - turned out to be nothing good even with Vista on top.

[KoHaN69]

Thanks for the input, alfaunits

What do you mean by "Ye. Try not to put it on a mirror, though." ?

Also, I disagree to killing the page file. I've had problems in Source games while doing that.

I've done some more research and seems RAID 0 is quite overrated, especially for gaming.

9.) If I have 3 drives, instead of putting 2 in raid I can make

Drive1 Partition1- System Partition2 - Storage
Drive2 Games
Drive3 Storage/Page file

and would not notice any realistic disadvantages to RAID 0
right?

[alfaunits]

What do you mean by "Ye. Try not to put it on a mirror, though." ?

PF on a mirror won't boost performance; on the contrary, the writes suffer a minor overhead. I doubt anyone would consider a mirror (RAID1) volume for the PF, so I was just adding that comment.

Also, I disagree to killing the page file. I've had problems in Source games while doing that.

I had problems if I had insufficient RAM (read: laptops).
BioShock?

I've done some more research and seems RAID 0 is quite overrated, especially for gaming.

It's not something you require for gaming, but it has no drawbacks vs. a single drive for gaming. Safety aside!

9.) If I have 3 drives, instead of putting 2 in raid I can make

Essentially, what you said is correct.

I myself can't imagine a single drive volume, because I move a lot of data often

[Serra]

I'm generally in agreement with Alfaunits suggestions, but I do have a couple of disagreements and/or elaborations to make...

1. Pagefiles on the same drive as the OS is "bunk"
I disagree. Lets say you follow what I consider to be "best practices" with hard drives - using a separate one for every "major" app (an application that itself uses enough hard drive resources to require its own) - which generally means just 1-2 other drives for desktops - then your OS disc isn't really don't a lot more than finding out where links point for you. There will be a few things, like it's probably where windows media player resides, but realistically it's heavily underutilized. The result of this is that it becomes advisable to put the page file on the same drive.

2. Pagefiles should be towards the middle of a drive...
Taking a slice out of the middle area of a drive for a pagefile (because they should have their own partitions) creates more issues than it solves on a desktop IMO. For one, it forces you to have at least 3 partitions on the drive instead of 2. It's just generally easier to put your page file at the start (physical outer edge) of the drive where it can have the best benefit in response time and be happy. The real fact of the matter is that at worst you're maybe looking at an 8GB pagefile, and 8GB on current drives is nothing in terms of loss of cylinders causing slower response to the next portion of drive.

3. In response to your question 5b, I think the answer we're looking for is "yes"... insofar as your OS will not see 2 hard drives in RAID, the OS will only see a single hard drive with a size equal to twice that of the constituent drives.

and yeah... I wish that hybrid drives were out this year too. It's stupid that we can't have even 1GB of flash memory on newer drives and instead have to wait until the drives are fully SSD.

[Serra]

And props to Stevecs - anyone who hasn't read his posts in here really should. He forwarded me this stuff earlier and I've been just terrible in terms of lack of response, but it really does need to be here. Every time I look at the e-mails he's sent me I start looking for a hosting solution for some of the documents, and eventually get derailed and forget about it. But I swear, someday I'll get to it.

[alfaunits]

1. Pagefiles on the same drive as the OS is "bunk"
I disagree.

Speed-wise it's bunk, on the same physical drive.
My suggestion was and still is: ditch the b***h and I won't snitch

2. Pagefiles should be towards the middle of a drive...

I think (hope) MS had speed in mind here, similar to NTFS's MFT zone placement, although, I still don't see how it would benefit a PF on a separate partition (mid-place on a single partition ye, but separate one..)

[Polizei]

And props to Stevecs - anyone who hasn't read his posts in here really should. He forwarded me this stuff earlier and I've been just terrible in terms of lack of response, but it really does need to be here. Every time I look at the e-mails he's sent me I start looking for a hosting solution for some of the documents, and eventually get derailed and forget about it. But I swear, someday I'll get to it.

Very patient guy who really knows his stuff. Emphasis on really. Great asset to the forums.

Walked me through using a RAID benchmarking program called IOZone. Im sure I stretched his patience to the limit with the stupid questions... after I got the answer, I always thought to myself, "Duh." In any event, HDTach and HDTune cant hold a candle to what IOZone can tell you about a RAID array. The only thing that IOZone doesnt tell you is access times and averages. Who needs em when IOZone outputs such comprehensive information? No one.

Ive told myself I would write a walk-through for IOZone, but college consumes all my time and I never get around to it.

[Serra]

Speed-wise it's bunk [to have a pagefile on the OS drive], on the same physical drive.
My suggestion was and still is: ditch the b***h and I won't snitch

One question: Why?

Again, assuming that your OS drive holds your OS and perhaps a few small programs that don't require disc access because you've followed best practices and put disc-intensive applications on their own discs (or on discs which hold programs which will not be in action at the same time), one of the only things your OS disc will do is point to shortcuts and start Windows. After that, it's just a sitting waste of cash. I can't think of a reason for the vast majority of people not to use it for this task, which will save you from having to buy another separate disc and absolutely will speed up some programs.

I think (hope) MS had speed in mind here, similar to NTFS's MFT zone placement, although, I still don't see how it would benefit a PF on a separate partition (mid-place on a single partition ye, but separate one..)

I think the MFT zone placement was the result of an engineering decision to allow the OS access to the outer portions of the disc to provide fastest boot-up and program access times (which would also be assuming that best disc practices were followed, naturally). It's generally placed just far enough outside that the core OS and a few programs can fit in front of it, and I'm not sure MS has really given it a second thought since its original implementation. I could be wrong about all that, but it's my strong theory.

The benefit to a PF on a separate partition is that your PF will only fragment on your system partition. Use a second partition (or drive) for your PF and you'll see it will never fragment. One does have to be careful when partitioning though to ensure that aside from, say, bootup one will not make extensive use of their system partition at the same time the PF partition would be necessary (if that were the case, it does belong elsewhere).

[IanB]

The benefit to a PF on a separate partition is that your PF will only fragment on your system partition. Use a second partition (or drive) for your PF and you'll see it will never fragment. One does have to be careful when partitioning though to ensure that aside from, say, bootup one will not make extensive use of their system partition at the same time the PF partition would be necessary (if that were the case, it does belong elsewhere).

I still strongly feel that a small separate partition at the start (fastest) of a separate drive purely for temp storage (change your TMP and TEMP system environment variables to point to there and all apps will use it), Internet cache and pagefile too is better, as this removes all disk contention from the OS and apps which may be being accessed at the time. Not to mention better organisation for easier management, like deleting redundant temp files which many apps leave which you don't want clogging up your fast OS drive. I recommended an ideal drive layout here. It is the Xtreme option if you have a spare drive, but will give fastest system response. You only need a couple of gigs for temp space and pagefile combined, maybe 5 or 6 max if you insist on a large pagefile.

As for the pagefile fragmenting, it will NEVER do that if you set the min/max values for the size on a single drive to be the same, as then the size is set and it never shrinks or grows. Then use PageDefrag (originally from SysInternals) to defrag that pagefile once for good, after fully defragging the partition you have set it on.

[alfaunits]

One question: Why?

Again, assuming that your OS drive holds your OS and perhaps a few small programs that don't require disc access because you've followed best practices and put disc-intensive applications on their own discs (or on discs which hold programs which will not be in action at the same time), one of the only things your OS disc will do is point to shortcuts and start Windows. After that, it's just a sitting waste of cash. I can't think of a reason for the vast majority of people not to use it for this task, which will save you from having to buy another separate disc and absolutely will speed up some programs.

You presume Windows doesn't touch the Windows drive at all, or ridicolous little - it does. Will you notice it DURING a game? Prolly not. Will you notice during game load? Very likely yes.
You will notice it during loading of programs that use shares DLLs on the OS drive - Office, etc.

I think the MFT zone placement was the result of an engineering decision to allow the OS access to the outer portions of the disc to provide fastest boot-up and program access times (which would also be assuming that best disc practices were followed, naturally). It's generally placed just far enough outside that the core OS and a few programs can fit in front of it, and I'm not sure MS has really given it a second thought since its original implementation. I could be wrong about all that, but it's my strong theory.

MS has made this decision in Windows XP I believe, and has given the reasons I mentioned: better overall MFT performance, i.e. file access times.

The benefit to a PF on a separate partition is that your PF will only fragment on your system partition. Use a second partition (or drive) for your PF and you'll see it will never fragment. One does have to be careful when partitioning though to ensure that aside from, say, bootup one will not make extensive use of their system partition at the same time the PF partition would be necessary (if that were the case, it does belong elsewhere).

Eeeh, not setting a fixed size for the PF is, IMO, not best practice. And if you set a fixed size - there won't be any fragments. If there are, set it to NONE, reboot, delete the pagefile.sys and recreate it (possibly defragment the drive).

[Serra]

I think you and I will have to agree to... well, not disagree... but strongly suggest people look at their usage habits evaluate for themselves, Alfaunits. With disc partitioning, that all I can ever say. I strongly affirm that the majority of users are just fine with the PF on the same disc as the OS - assuming they'll use a separate disc for primary programs. The purchase of a separate hard drive is very hard to justify for the minuscule difference that well over 90% of the population would see (IMO).

As far as setting PF min/max - as stated in the post, I do personally suggest giving it a fixed size (and, you'll notice, I also state that if you do have a spare disc or disc that won't see conflicting use with it, to put it there... but again, I wouldn't go so far as to tell people to buy a separate HDD *just* for it). It won't fragment over the hard drive, but as to internal file fragmentation within the size zone - that's another matter. The Microsoft best practice is to put it on its own partition, and so I've got to mirror that sentiment.

[alfaunits]

Oh, I wouldn't suggest for Average Joe Surfer to buy separate HDs. I was talking about gamers, and most ppl on this forum - who already have more HDs, some of which are simple storage... to use that. Heck, for <100USD/500GB today.... seriously!
Heck, Average Joe up is more likely to have problems separating things than keeping it all together

[karateo]

Hi!
I created an raid-0 array using 2x WD 250KS disks
I chose stripe size 32k and allocation unit while formating 64k

It's only a 5Gb partition at the beginning of the disk with 130mb/sec average read and 8.3ms average access

I am going to use it ONLY for my windows XP/Vista pagefile.

Do you think I chose the right stripe size?
I have read that 64k is the recommended allocation unit for pagefile, but I didn't find anything about the strip size. I thought, that using 32K i will cause its cluster to separate to both disks

[Serra]

Asking a question like that is like asking a room full of guys what their definition of a hot girl is - the answer will vary from person to person by usage pattern.

There are some generalizations that can be made, such as smaller numbers for smaller files... but there's no cut-and-dry "right" answer. In most cases, I generally suggest trying it both ways and then think to myself "Not that it matters, it's going to end up being a completely subjective/biased answer whatever they come up with because the difference isn't generally noticeable".

IMO: Stick with defaults and be happy, unless you're setting it up for benching or some special application - if so, then you can tweak for that application.

[Knight]

Serra, I have a question about my Intel Matrix Array. I would like to apologize if the question does pertain to the reason for creating this great thread.

I created two volumes by using two 320GB 7200.10 drives. Both volumes are set in Raid 0 through the Matrix control panel during boot. I am using the ICH9R south bridge.

Volume 1 - 107GB OS and Applications
Volume 2 - 496GB Storage

I believe that my volumes are limited due to the results from HD Tach (Not the best, I know ). The image below is from Volume 1 without Volume Write Back Cache. It seems to have the performance of only one drive.



The one below is with VWBC enabled. It has a significant increase, but seems to be caped. Others with a similar setup are running the test on the whole 640GB and getting a read speed of 180-200.



The volume is clean of errors and I followed Seagate's instructions on enabling SATA2 (Jumper setting). The Intel Raid Manager (v7.8) reports a healthy array. I haven't had any errors or corruption of the OS with the array like this, but I would just like to know a little about what might be the problem, or if this is normal.

[Serra]

That's a good advertisement for enabling WBC.

I seem to recall that Seagate 7200.10 drives usually get ~80MB/s max out of the first portion of the drive, so if you're seeing ~160MB/s with two drives, I'd probably be pretty happy. Still, if you can provide links to other people doing noticeably better we can take a look at them and try to determine what may cause the differences.

[Knight]

That's a good advertisement for enabling WBC.

I seem to recall that Seagate 7200.10 drives usually get ~80MB/s max out of the first portion of the drive, so if you're seeing ~160MB/s with two drives, I'd probably be pretty happy. Still, if you can provide links to other people doing noticeably better we can take a look at them and try to determine what may cause the differences.

I guess that my results are typical then. I just took a look in the Hard Drive Benchmark thread to find the picture that I was interested in posting. I however found this:

http://www.xtremesystems.org/forums/...&postcount=187

I believe that if I were to use three drives then it would scale in similar manner.


EDIT:

It could also be due to the firmware being bad. Some 7200.10's have the 3.AAK firmware. Most of those drives perform less than the other similar drives with a different firmware.

http://forums.vr-zone.com/showthread.php?t=213448
http://www.tomshardware.com/forum/24...agate-firmware

My luck gave me two 3.AAK drives.

[swiftex]

i use 8gb's of ram so I just ditched the pagefile period.

some guys may want 2mb allocated for a dump file but &*(^&#37;$ I don't bother

pagefile and prefetch gone way of dodo bird...........

[MediumRare]

Sorry to bring this back from a 2 month hibernation but it's such a awesome thread that I don't think most will mind. I'm in the middle of a new build, see specs below, and I purchased two wd6400aaks 640gb drives with the intention of putting them in a RAID 0 config. This build will be mainly used for gaming, surfing and normal family use.

1) After reading the info in this thread am I correct in coming to the conclusion that RAID 0 would not be much of a benefit for this system?

2) Would I be better off using RAID 1 and enabling elevator seek since it was stated, "Use RAID-1 when: You have a game or application that would greatly benefit from a reduction in seek time (lots of small file reading going on)"

2a) Total rookie question regarding drives but if the answer to #2 is yes then how does one enable elevator seek.

3) I also have a 160GB SATA drive laying around not being used so would I be better off ditching any type of RAID and having both my WD 640's as separate drives and doing something like this:

WD 640 #1: 15GB-20GB partition for OS / rest of drive for storage, backup
WD 640 #2: Partition w/ Games & Apps / partition with Documents (photos & music)
160GB: 6GB partition for page file / rest for whatever

Any help would be greatly appreciated. I really thought gaming performance would be increased using RAID 0, glad I stumbled upon this thread.

[IanB]

You can't "enable" elevator seek. It's an algorithm that's either used by your RAID controller to manage RAID1 volumes or it's not, it's a function of the controller firmware.

FWIW, I'd RAID1 the 640Gb drives and use the 160Gb spare as your pagefile/temp drive (small first partition) with the rest for less critical data storage. Make a small OS/apps partition on the RAID1 then put documents etc. you'd consider critical and worth backing up in the rest of the space, so you have the RAID redundancy for that. To use the spare drive for temp files, set the environment variables TEMP and TMP to point to the drive (right-click My Computer, Properties/Advanced/Environment Variables, set for all users and the separate system ones too). Putting your Internet cache there and away from your OS wouldn't be a bad idea either. That way you have spare spindles always available for writing temp files etc. and the RAID set interface doesn't become a bottleneck.

Other people will have other ideas I'm sure. There's probably no wrong way to use the two drives, but RAID1 will give you more security over outright speed, and with those drives you already have great baseline speed anyway. It doesn't matter if the 160Gb drive isn't a screamer, you don't really need the speed for temp stuff, just the ability to access in parallel with other file I/O should help improve system responsiveness.