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How to get 350 MB/s read out of Raid 0

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June 26, 2011 2:33:09 PM

SSDs are too expensive and have a little storage, i've considered to buy 4 WD caviar Blue 500 GB Sata 6 Gb/s and operate them as Raid o to get the maximum read & write speed of them, seen a lot of benchmarks with 2 and 3 hard drives in raid 0 but average read is between 150-180 max.
and have seen also that full size of disks in raid 0 are have got lower average read speed then a specific size of the strip array ( such as 100 Gb ) which showed about 329 MB/s read !!!
anyone have an explanations and clarifications of this, would appreciate his help !
Thanks in Advance

More about : 350 read raid

a c 104 G Storage
June 26, 2011 4:48:07 PM

Hello,

If you are setting up a software RAID-0 for speed of reading and writing, 2 - 5 Disks are optimal. Remember that with 4 RAID-0 drives, you have 4 times the risk of losing your data if any one of them individually goes bad. As a general rule with RAID-0 the speed is x times the number of disks in the volume.

My recent thoughts for fast loading, calculations, adequate storage, speed, is to have an SSD (doesn't have to be so big), then use mount points to empty named folders for HDD storage.
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a c 82 G Storage
June 26, 2011 4:59:32 PM

More hard disks provide better performance. If 3 drives in RAID 0 provide 150-180 MB/s, then 5-6 drives should meet your performance criteria. On the other hand, RAID 0 is not meant to be used for long time storage as the risk of losing all data increases with the number of drives.

Even though it's 4 years old, this article should be helpful: javascript:%20validform(this);http://www.tomshardware.com/reviews/RAID-SCALING-CHARTS...
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a c 415 G Storage
June 26, 2011 5:16:59 PM

ilysaml said:
SSDs are too expensive and have a little storage, i've considered to buy 4 WD caviar Blue 500 GB Sata 6 Gb/s and operate them as Raid o to get the maximum read & write speed of them
You need to understand that the biggest benefit of SSDs is the fact that their access times are about 100X faster than that of a hard drive - and that RAID does not improve access times (it only improves the transfer rate). That means that RAID will not help very much with the kinds of tasks that require accessing a lot of small files, such as booting your system or starting up programs.

I'm not saying you shouldn't use RAID, just that you should know what it can and can't do for you before you go to a lot of effort setting it up. Also - don't forget that you're more likely to lose all the data on a RAID-0 volume, so it's even more important to have a sound backup strategy in place.
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June 26, 2011 5:31:58 PM

John_VanKirk said:
Hello,

If you are setting up a software RAID-0 for speed of reading and writing, 2 - 5 Disks are optimal. Remember that with 4 RAID-0 drives, you have 4 times the risk of losing your data if any one of them individually goes bad. As a general rule with RAID-0 the speed is x times the number of disks in the volume.

My recent thoughts for fast loading, calculations, adequate storage, speed, is to have an SSD (doesn't have to be so big), then use mount points to empty named folders for HDD storage.

i don't care about data loss, i will be backing -up regularly to an external storage, i'm running 7 x64 i'm a hardcore gamer so the C partition gets 200 GB when i install software, games and windows updates
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June 26, 2011 5:34:16 PM

GhislainG said:
More hard disks provide better performance. If 3 drives in RAID 0 provide 150-180 MB/s, then 5-6 drives should meet your performance criteria. On the other hand, RAID 0 is not meant to be used for long time storage as the risk of losing all data increases with the number of drives.

Even though it's 4 years old, this article should be helpful: javascript:%20validform(this);http://www.tomshardware.com/reviews/RAID-SCALING-CHARTS...

link you provided is not working, and i don't care about data loss, i will be backing up regularly
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June 26, 2011 5:37:15 PM

guys, i transfer a 7 GB movie in 8 minutes between internal disk drives, what should i do to get the max performance with a low cost benefit ???
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Best solution

June 26, 2011 5:44:59 PM

Raid-0 makes access time worse because a file spanning more than one stripe - including because it doesn't start at the stripe - has to wait for several platters instead of one, and the platters can't be synchronized, especially since their number of sectors per track is optimized individually now.

As a mean value, you wait for 2/3 platter rotation instead of 1/2 (plus arm movement), losing 1/6 turn or 1.4ms. If two disks read at 260MB/s instead of 130MB/s, the breakeven is at 360kB.

If your machine requests many accesses simultaneously, which is especially the case since Win XP and its Prefetch, then smaller files in big stripes can be on separate disks and be delivered in parallel, but most Bios offer only 128kiB maximum stripe size, which is too little for present disks.

So Raid-0 brings speed ONLY on really big files, like 500kB and more. You do feel a nice improvement on pictures, especially if uncompressed. But to start Windows, whose mean file size is around 150kB and makes even smaller accesses, Raid-0 uses to be slower than a single disk.

If you have such uses, take a Raid, yes - but complete it with a small SSD for the OS.

AND align your volumes! It makes a big difference on pre-Vista Win, where the first volume starts at sector 63, hence Ntfs clusters often start with 1 sector on one disk and the next ones on the other disk... With Fat32 (undesirable for safety and security) alignment is more complicated, please see
http://www.msfn.org/board/topic/151798-does-fat32-align...
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June 26, 2011 5:49:35 PM

To transfer 7GB movies, make a Raid-0, yes.
I believe (please check) that Win7 begins all volumes at multiples of 1MiB. Since Ntfs aligns its clusters with the volume, it should be fine.
Choose your disks for low mean access time, since the throughput will be good.
Good individual throughput depends on rotation speed and on capacity PER PLATTER.
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June 26, 2011 5:57:16 PM

Pointertovoid said:
Raid-0 makes access time worse because a file spanning more than one stripe - including because it doesn't start at the stripe - has to wait for several platters instead of one, and the platters can't be synchronized, especially since their number of sectors per track is optimized individually now.

As a mean value, you wait for 2/3 platter rotation instead of 1/2 (plus arm movement), losing 1/6 turn or 1.4ms. If two disks read at 260MB/s instead of 130MB/s, the breakeven is at 360kB.

If your machine requests many accesses simultaneously, which is especially the case since Win XP and its Prefetch, then smaller files in big stripes can be on separate disks and be delivered in parallel, but most Bios offer only 128kiB maximum stripe size, which is too little for present disks.

So Raid-0 brings speed ONLY on really big files, like 500kB and more. You do feel a nice improvement on pictures, especially if uncompressed. But to start Windows, whose mean file size is around 150kB and makes even smaller accesses, Raid-0 uses to be slower than a single disk.

If you have such uses, take a Raid, yes - but complete it with a small SSD for the OS.

AND align your volumes! It makes a big difference on pre-Vista Win, where the first volume starts at sector 63, hence Ntfs clusters often start with 1 sector on one disk and the next ones on the other disk... With Fat32 (undesirable for safety and security) alignment is more complicated, please see
http://www.msfn.org/board/topic/151798-does-fat32-align...

if RAID 0 will make access time sucks, i won't go for it cuz i'm using Photoshop CS5 and a lot of other applications that i need them to be faster so how will i get as an average of 200 MB/s of read and Write, all i need is to see data transfered like a charm and no waiting anymore. If i use SSD, what model and size should i go for, i'm so confused
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June 27, 2011 5:46:43 AM

Ok then, consider this. A solid state drive, Crucial M4, for your OS, or better yet, two Crucial M4's in RAID 0 for your OS with weekly cold backups to a backup drive. Four disk drives, WD RE4's, configured as two RAID 10 arrays, the outer 250gb (62.5gb each drive on the outer edge) for your home directory, the remaining as storage.

I'm using a hardware RAID card that connects to 8 SATA drives. Because I'm not playing around with drives any more. My goal is to run two Crucial M4's in RAID 0, as I said above, and 6 WD RE4's in two RAID 10 arrays. I only need the SSD's and two more WE4's to make this happen. I'm also using two externally mounted internal SATA drive boxes. The drives function as if they were mounted inside my case.

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June 27, 2011 5:50:26 AM

i think i'll go for SSD, one last question if i get SSD drive rated as 350 MB/s read and 225 MB/s write and normal HDD rated as 126 MB/s at Max, how they should work together ?
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June 27, 2011 3:38:07 PM

Something is wrong if it takes 8 minutes to copy a 7GB file from one drvie to another. That is very slow. Should take less than 2 minutes. Find out what your problem is first.
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June 27, 2011 8:39:52 PM

turk_1000 said:
Something is wrong if it takes 8 minutes to copy a 7GB file from one drvie to another. That is very slow. Should take less than 2 minutes. Find out what your problem is first.

Processor is 2% usage while moving the movie to the other partition, rams ar 35% usage while doing so, games runs great and smooth without a problem, so it's the problem of the HDD i guess, as the electricity went out a lot of times this might cause a shock to the HDD
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a c 82 G Storage
June 27, 2011 9:51:04 PM

Are moving movies from one partition to another partition on the same hard disk? If so, then it's normal. Copying to a different hard disk should be much faster. Creating several partitions on a single disk usually doesn't improve performace.
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June 27, 2011 9:54:13 PM

doesn't make sense, cuz i used to transfer larger files with less time than that with my last samsung HDD, i think i'm going for an SSD, but need someone to clarify some stuff which includes what about the difference between average speed of Reads and Writes with SSD and HDD ?
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June 28, 2011 12:11:50 AM

ilysaml said:
doesn't make sense, cuz i used to transfer larger files with less time than that with my last samsung HDD, i think i'm going for an SSD, but need someone to clarify some stuff which includes what about the difference between average speed of Reads and Writes with SSD and HDD ?


SSD's today are very much faster at reading and writing many smaller files. For large files, SDD's can be faster, perhaps a lot faster. However, I'm running 4 WD RE4's in RAID 0 and am getting over 500MB/s for reads and writes for large files (sequentially accessed data.)

While I will be buying two SSD's to run in RAID 0 for my OS partition, SSD's aren't everything you might want them to be. The more you study them, the more you will see that they have issues. The answer is to use both IMO. But I will never use a single HDD again unless it's a backup drive.
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June 28, 2011 7:35:23 AM

r0ck3tm@n said:
SSD's today are very much faster at reading and writing many smaller files. For large files, SDD's can be faster, perhaps a lot faster. However, I'm running 4 WD RE4's in RAID 0 and am getting over 500MB/s for reads and writes for large files (sequentially accessed data.)

While I will be buying two SSD's to run in RAID 0 for my OS partition, SSD's aren't everything you might want them to be. The more you study them, the more you will see that they have issues. The answer is to use both IMO. But I will never use a single HDD again unless it's a backup drive.

what about access time and data loss ? did u suffer any of that ?
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June 28, 2011 7:16:40 PM

ilysaml said:
what about access time and data loss ? did u suffer any of that ?


In my 4 drive RAID 0 array? No but I make weekly backup images of that RAID partition. I have two more partitions in RAID 10. Access times for RAID arrays will not increase and might decrease but I'm still getting a little over 6ms average for my disk drives. I will make a posting when I am able to buy the SDD's, probably Crucial M4's. You can't trust RAID 0 but you can't beat the performance.
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June 28, 2011 7:22:15 PM

thx for all your information, i'll go for high speed SSD i guess
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June 28, 2011 7:22:49 PM

Best answer selected by ilysaml.
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