Re: Recomended FS
От
Markus Wollny
Тема
Re: Recomended FS
Дата
Msg-id
2266D0630E43BB4290742247C891057502B9D2C9@dozer.computec.de
Список
Дерево обсуждения
Re: Recomended FS Christopher Browne <cbbrowne@acm.org>
> Theory vs. real life. In Theory, RAID5 is faster because less > data have > to be written to disk. But it's true, many RAID5 controllers > don't have > enough CPU power. I think it might not be just CPU-power of the controller. For RAID0+1 you just have two disc-I/O per write-access: writing to the original set and the mirror-set. For RAID5 you have three additional disc-I/O-processes: 1. Read the original data block, 2. read the parity block (and calculate the new parity block, which is not a disk I/O), 3. write the updated data block and 4. write the updated parity block. Thus recommendations by IBM for DB/2 and several Oracle-consultants state that RAID5 is the best compromise for storage vs. transaction speed, but if your main concern is the latter, you're always best of with RAID0+1; RAID0+1 does indeed always and reproducably have better write performance that RAID0+1 and read-performance is almost always also slightly better.
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