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RAID 10 Block Size

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lelliott731

[H]ard DCOTM April 2017
Joined
Mar 15, 2002
Messages
941
Hey guys, I am setting up a Dual Athlon MP 2800+ system with 4x160GB Seagate SATA hard drives on a 3Ware Escalade 8506-4LP. I want to run RAID 10, because it gives me much higher transfer rates then RAID 5. I just don't know what block size to use. It is going to be mainly used as an Exchange Server, Sharepoint Server, and Office Live Meeting server. The options are 64k, 128k, 256k, 512k and 1MB. It might do some web hosting, but that is not going to be it's major role. With 64k as it's initial size, these are the results I got using SiSoft Sandra 2004 SP2b:
Drive Index (MB/s) 101
Buffered Read (MB/s) 167
Sequential Read (MB/s) 117
Random Read (MB/s) 105
Buffered Write (MB/s) 61
Sequential Write (MB/s) 61
Random Write (MB/s) 56
Average Access Time (ms) 1

Thanks in advance for any help you guys might have.
 
what is the average file size you're going to use? Ideally you want the block size as large as possible, but closest to a multiple of your average file size. For example. with a block size of 64K, a 31K file and a 63K file both occupy the same amount of space on the disk... In a 32K block size, the 31K file can be in 1 block, but the 63 is in 2... Instance 1 has wasted space, instance 2 is rather efficient. Of course this varies from system to system. Overall you may receive better performance with one over the other. I leave it at the default and call it a day, however.
 
sisoft is _NOT_ a real benchmark for hdds. look into iometer if you really want to benchmark it, but the best way is try it. the raid _is_ only a data array, right? so just try it and see, with reformats in between. do you really need the transfer rates? this application sounds like a mail server type, with lots of little reads and writes, where smaller block sizes (8 or 16k) are good.
make sure the filesystem block size matches the raid block size.
 
How do you make sure that the file system block size is the same as the RAID array's size? I was just planning on using NTFS, do you know what block size that uses?
 
look at the format dialog where it says "allocation size" or something like that. it may not go large enough to match the raid device block size, in which case just make it as big as possible. (eg if your raid is in 128k chunks, the ntfs may only go to 64k block size.) however, for this i'd recommend a small block size, like 32 or even 16k. but that's just a guess, unless you're in a big hurry, try it and see what works best.
 
I didn't see any allocation size option in the format screen when I installed Windows. Where is it located?
 
it's not part of the windows setup -- only an advanced option when formating manually.
 
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