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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The Thursday 2006-11-09 at 15:54 -0500, Greg Freemyer wrote: ...
I don't know the details of how linux implements it but conceptually for the worse case with raid 5 (ie. scattered writes) to update a single block you have to:
Read original block (even if your updating it 100%) Read Parity Block Back-out the original block from the parity calculation (Simple XOR logic) Put the new blocks data into the parity calculation (Simple XOR logic) Write the new data block Write the new parity block
So it takes 4 i/o's to do a single logical write assuming scattered disk writes.
Question. The data block, is it written to one disk, or is it split over two disks? - -- Cheers, Carlos E. R. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux) Comment: Made with pgp4pine 1.76 iD8DBQFFU7jDtTMYHG2NR9URAu7VAJ9aS9viuUdUFgrAJShtw5PqL8wJ9gCgiEMv ocUV0QEHvUS6MZd8H7w50vg= =gFwg -----END PGP SIGNATURE-----