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1. Re: Harm, looking for a quick answer on a RAID question...
Harm Millaard Dec 1, 2011 7:15 AM (in response to davidbeisner2010)David,
This may be informative: http://www.tomshardware.com/reviews/wd-4k-sector,2554-3.html
With a sector size or cluster size of 4 KB, data are distributed across the partition in 4 KB parts. Suppose you have a 10 KB file, three full clusters will be occupied: 4 KB - 4 KB - 2 KB. The remaining 2 KB is called slackspace and can not be used by other files. With a block size (stripe) of 64 KB, data are distributed across the array disks in 64 KB parts. Suppose you have a 200 KB file, the first part of 64 KB is located on disk A, the second 64 KB is located on disk B, the third 64 KB is located on disk C and the remaining 8 KB on disk D. Here there is no slackspace, because the block size is subdivided into clusters. When working with audio/video material a large block size is faster than smaller block size. Working with smaller files a smaller block size is preferred.
Sometimes you have an option to set 'Chunk size', depending on the controller. It is the minimal size of a data request from the controller to a disk in the array and only useful when striping is used. Suppose you have a block size of 16 KB and you want to read a 1 MB file. The controller needs to read 64 times a block of 16 KB. With a chunk size of 32 KB the first two blocks will be read from the first disk, the next two blocks from the next disk, and so on. If the chunk size is 128 KB. the first 8 blocks will be read from the first disk, the next 8 block from the second disk, etcetera. Smaller chunks are advisable with smaller filer, larger chunks are better for larger (audio/video) files.
What you see as 'sector size' from Windows is better called the block size and for video you can best choose the maximum, in this case 64 KB.
BTW, also have a look at Adobe Forums: How to access more than 2 TB of disk...
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2. Re: Harm, looking for a quick answer on a RAID question...
davidbeisner2010 Dec 1, 2011 8:21 AM (in response to Harm Millaard)Thanks, Harm... so the 4k that the hardware RAID configuration asked me to set was the sector or clustor size, and the Windows volume was asking for the chunk size, which I set at 64k. So the software will read/write 64k chunks, and the hardware will direct those into 4k sectors?
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3. Re: Harm, looking for a quick answer on a RAID question...
Harm Millaard Dec 1, 2011 8:43 AM (in response to davidbeisner2010)Correct.
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4. Re: Harm, looking for a quick answer on a RAID question...
davidbeisner2010 Dec 1, 2011 1:21 PM (in response to Harm Millaard)Glad I understand how it works now! :-)
In transferring all my data from my internal three-disk RAID-0 to this new external four-disk RAID-5, my sustained transfer speed has been about 105MB/second. Does that sound about right?
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5. Re: Harm, looking for a quick answer on a RAID question...
Harm Millaard Dec 1, 2011 2:09 PM (in response to davidbeisner2010)How is that G-raid connected? A 3 disk raid0 should achieve around 300 MB/s, a 4 disk raid5 on a good controller will achieve around 255 MB/s so from that perspective 105 seems low, but if it works over an eSATA or network connection, it makes sense. If it is over a 8087 or 8088 multilane cable it is low.
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6. Re: Harm, looking for a quick answer on a RAID question...
davidbeisner2010 Dec 1, 2011 2:26 PM (in response to Harm Millaard)It's hooked up with an esata cable using the gtech pci express raid card... It peaked around 340mb for a short time, but then settled at 105... It's still running about the same speed as my internal drives, so I guess all is well...



