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OS6 now works on x86 Legacy WARNING: NO NTGR SUPPORT!
Update: It is now unofficially possible using NTGR images to update legacy hardware to os6.X See Post #3, for directions to install 6.2.1 on x86 Ultra and Pro Models. (ARM NOT SUPPORTED by this OS) ...
mdgm and I have decided that its time to lock this thread. So please do post any new OS6 on Legacy issues on their own threads.
I'm not sure if this is really a question about BTRFS or RAID.
If you are updating a sector on a RAID-1 array, the general case is that you need to read the sector, update the part that's changing, and then write it - you need to do that on both drives.
Of course the read/write operations are cached - but if the I/O is random, that will not help.
If you are updating a sector on a RAID-5 array, the I/O is the same in the general case. The data sector is read/updated/rewritten. The parity sector (on a different drive) is read, and updated, and written. The parity sector is updated by XORing with the original data, then XORing again with the changed data.
So in the general case of making a small update (less than one sector), the I/O for RAID-1 and RAID-5 are the same.
But there is a special case- when you are writing the entire sector on the application layer.
For that, RAID-1 simply writes the data to both drives - no reads are required.
RAID-5 still requires the general case - the data sector still needs to be read, because the parity sector needs to be XORed with it. Likewise, the parity sector needs to be read.
The impact on speed depends on performance of the disk caching.
If you are updating a sector on a RAID-1 array, the general case is that you need to read the sector, update the part that's changing, and then write it - you need to do that on both drives.
Of course the read/write operations are cached - but if the I/O is random, that will not help.
If you are updating a sector on a RAID-5 array, the I/O is the same in the general case. The data sector is read/updated/rewritten. The parity sector (on a different drive) is read, and updated, and written. The parity sector is updated by XORing with the original data, then XORing again with the changed data.
So in the general case of making a small update (less than one sector), the I/O for RAID-1 and RAID-5 are the same.
But there is a special case- when you are writing the entire sector on the application layer.
For that, RAID-1 simply writes the data to both drives - no reads are required.
RAID-5 still requires the general case - the data sector still needs to be read, because the parity sector needs to be XORed with it. Likewise, the parity sector needs to be read.
The impact on speed depends on performance of the disk caching.
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