Jump to content
Corsair Community

Format RAID 0 X32's with 32/64kb allocation size


Recommended Posts



I have two X32's set up in raid 0 and am experiencing some unexpectedly relatively poor performance from the o.s. partition on the array.


I have the drives split into a 25Gb o.s partition and a 34.6Gb partition for installed software to run from. I created the array using 128k stripe but can't for the life of me manage to find a method or piece of software to allow me to choose the allocation size for the format as all of the software I have found either doesn't see the array or doesn't allow me to set the allocation size.


Thanks in advance for any help as I want to rule out any setup issues before going down the rma route.

Link to comment
Share on other sites

The best way to set up for a RAID 0 is when doing a clean install. I can definately help you out here. I advise against (very much) using alternate programs as converting the clusters with a current install will lead to a lot of filesystem errors that will have to be repaired. I would also advise against multiple partitions with SSDs in RAID0. Doing this with normal HDDs was for performance advantages (aka shortstroking) and would be overkill with SSDs.


With the stripe at 128k, you want to use a 32k allocation unit (aka cluster size). To do this properly, you will have to create a small partition with the default allocation of 4k for the Windows bootloader. If you are using Win 7, you can use the System Reserved to run the bootloader.


Fire up your Windows install and partition your drives like so:


[100MB*] [Remainder of the drive]


* Win7 System Reserved default size


For Vista/Win7, when you get to where you tell Windows where to install, hit Shift+F10 to open a command prompt. Type "diskpart" (no quotes) and hit enter. Type the commands in as follows.


>list disk

(Find your RAID - make sure you install your drivers first :idea:)

>sel disk #

(#=number for your disk. More than likely it will be 0)

>list partition

(you should see both partitions made)

>sel partition 1

(Win7 Sys Reserve/partition you created)


(tells BIOS "look here for bootloader" - very important)


(only if using Vista. Disregard if Win7 created the partition)

>sel partition 2

(now to the partition where Windows will actually go)


(This will get your customized cluster size)


(mounts the drive to a letter for the next step



When you get back to the command prompt, run chkdsk and make sure it reports back 32k clusters.


Lastly, proceed with install.


Let me know if it works.

Link to comment
Share on other sites

Thanks for the quick reply nfinite, the reason for the partitions is to keep the size of the o.s. partition backup as low as possible, Am I right in assuming that this shouldn't impact on performance anyway?


Have followed your instructions and there is an increase in performance yet still not where I'd expected them to perform, the read is good but write performance seems low.


Also, seems strange that the write performance is higher in the lower range of the benchmark.




Link to comment
Share on other sites

Right, I think I've found the root of the problem, my o.s. partition (Windows 7), even after being quick formatted with 64k allocation size reverts to 4k allocation size once windows is installed.


I am now trying to find a way of converting this back to 64k as none of the software I have or found "see's" my raid array to allow me to do this.


Does anyone else have the same problem?

Link to comment
Share on other sites

When you reinstalled Windows, did you have no partitions on the drive?


If you have partitions on it already, it won't create the System Reserved partition when you go through the install.


The instructions I posted are what I used with my Caviar Blacks in RAID. I did have to run a full format for it to take but it's important to do with normal HDDs, espcially brand new.


(100MB Sys Reserve, NTFS 4k, Active)

(1.8TB NTFS 32k)


For obvious reasons, DO NOT FULL FORMAT THE SSD.


Do a secure erase with GParted or HDDErase on both drives, put them back into RAID, install again and follow those instructions and you should be solid.


I will not recommend 3rd party tools to resize the drive, as they will cause errors and your system will not be able to boot.


Quick note - when you get the the screen asking where you want Windows to get installed, partition the drive there so it will create the System Reserved, then proceed to the command prompt and follow those instructions I posted.

Link to comment
Share on other sites

Thanks again for your help nfinite.


Right, deleted the array and used gparted to initiate the internal secure erase command on both drives, got Windows 7 installed as per your instructions with 4k allocation 100mb boot partition, balance of drives 32k allocation, read speed is a little slow in the lower range but picks up nicely in the bottom half of the ATTO bench.


The write however is still way below what I would expect from these drives in raid 0, anyone have any suggestions or do I have 1 or 2 faulty drives?

Link to comment
Share on other sites

My write speeds were still way down on what I expected so I backed up the then deleted the array, set my controller to ahci and using gparted wiped both drives with the internal secure erase command.


I've then changed both sata cables for two brand new sata II cables and done a fresh install of Windows 7 to a partition on my spinning drive. Then tested both x32 ssd as individual drives in ahci mode against one of the other partitions on my spinning drive, results below.




The one on the left and the one in the middle are the x32's, the one on the right is the spinning partition.


To say I'm dissappointed with the write speeds being slower than my spinning drive right across the test range is a bit of an understatement, and suggestions anyone?? :(:

Link to comment
Share on other sites

  • Corsair Employees

The test results he posted for for individual drives and they are performing properly according to the screen shots he posted.

Post an ATTO Screen shot of the raid array? Also how are you setting the Raid?

Should be 128K Cluster size for the Raid and 32k Allocation for the format.

I've then changed both sata cables for two brand new sata II cables and done a fresh install of Windows 7 to a partition on my spinning drive. Then tested both x32 ssd as individual drives in ahci mode against one of the other partitions on my spinning drive, results below.
Link to comment
Share on other sites

Sorry for creating confusion, it would appear that there is some disparity in the way retailers are advertising your products, they seem to be copying and pasting the specs related to the drives directly from your product overview quoting figures up to 240mb sequential read 170mb sequential write rather than listing the performance figures relating to the specific drive.


It's not the end of the world as the real world performance is still very good, I was just expecting to achieve somewhere near the figures quoted by the retailer in synthetic benchmark (for what that's worth).


That'll teach me to research the product before taking the plunge :o:

Link to comment
Share on other sites

  • Corsair Employees

NP and the SSD's will still have much better read performance and the access time is still much less than a spinning HDD.

I would suggest you use the spinning HDD for the swap file though and install the O.S. on the SSD for best over all performance.

Link to comment
Share on other sites

Right, wiped the drives and set them back up in a single array 128k stripe with 32k allocation size and these are the results, pretty much consistent with the information you've given me, I won't be sending them back but will drop them an email outlining their less than accurate description.




Thanks all for your help ;):

Link to comment
Share on other sites

  • Corsair Employees

NP and you can get the spec for the drives from our web site Under the resources Tab in the future sorry if I sound smug but in case someone else reads this.

I am sure the reseller just did not see that the performance was different for smaller drives and maybe only posted the spec for the X256 which is faster. Sorry about that we do try to police resellers but honestly its hard just trying to keep up with my self and what I am responsible for. I am fairly sure it was an honest mistake on their part and please let me know if they do not correct it who they are and what not I will sick our Sales manager after them.

Link to comment
Share on other sites

No worries, I bought the drives from two different resellers (stock issues).


1st was from Adam Carpenter (Uk), item link :- http://www.adamcarpenter.co.uk/corsair-extreme-series-32gb-sata-ii-solid-state-drive.html


the 2nd drive was from Dabs.com (Uk), item link :- http://www.dabs.com/products/corsair-memory-32gb-2-5-ssd-sata-300-64mb-64HY.html


Thanks again for all your help ;):

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...