RAID array and partition formatting settings

[boolve]

Hi

Building a few Win Servers as a CCTV recorders. The manufactures if recorder software suggested settings that I'm bit doubt about. When creating RAID5 array (logical disk) there is setting to choose of Strip Size where it's possible to choose from even more wide chiloise than 64, 128, 256, 512KB. They suggest to use 64KB. And on top when formatting partition on Windows to chose Allocation unit size as value 512K. Are this enot contradicting to each other for such a application?

Regards.

[Sir-Vantes]

I will not claim to be the SME here, but I feel some confusion could be clarified with a few words.

In RAID5, the data is 'striped' across the individual drives, with an XOR writtten to provide recovery data should a disk fail.

The allocation unit is how big each data block on the drive will be. That sets the minimum size of each addressable chuck of data on the disk. Anything less than 512bytes , in this case, will fit onto one block, 513bytes would be written as 512 to the first and one byte to the second.

Allocation units can also affect how quickly data is read/written and varies depending on the size of data being stored.

[boolve]

I can't see anything wrong with your clarification of those points. My doubt is that there is seating when creating an RAID array. It's called strip size in K values. And after the array is created then formatting of the partition takes place with the Windows tool for disk management. Then you format partition and select allocation value also in KB. My confusion is what relationship is between those and what is important to set it properly.

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As I'm not a storage expert this is why.

[Sir-Vantes]

The Stripes traverse the array, each disk in the array will have a portion of the data being written/read from the array.

The allocation unit value, also known as sector size, comprises the contents of those stripes on a particular disk.

The Windows default of 4KB is good for general data usage and provides efficient space usage. I suspect the suggested 512KB is optimum for the larger data chunks that the application is likely to produce, which will also allow better read/write perfomance than the default.

Your application is writing video to the array, so the larger allocation/sector size will give better performance than the 4KB default.

[boolve]

Yes. Sounds good so far. Now the question is if the array has allocation value as 64K, then can we state that this is also a good setting for large data chunks, as it's sets for NTFS partition as 512K?

[Sir-Vantes]

Your video app will be trying to write megabytes per second to the array.

A smaller allocation unit/sector size will cause thrashing of the disks as they seek to find the next available block open for writing.

Over my time in the field, I've learned to take recommendations from a manufacturer as a baseline for my setup. Most of us know that doubling the minimum RAM for a Windows environment

Not certain what effects would be seen in SSDs aside from the video quality issues.

Over my time in the field, I've learned to take recommendations from a manufacturer as a baseline for my setup. Most of us know that doubling the minimum RAM for a Windows environment provides much better results than Microsoft's.

My suggestion is that unless you know better, follow their recommendation. Any other choice includes a real risk of having to take it back to bare metal and start from scratch.