[操作疑難] 點解 RAIDZ2 要 6 隻碟?

因為多 d 碟位用?定係有其他原因呢?點解多數都話 5 隻碟用應該用 RAIDZ?

過低數量的話儲存容量效率唔高……

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本帖最後由 garywongwm 於 2016-10-31 12:19 編輯
因為多 d 碟位用?定係有其他原因呢?點解多數都話 5 隻碟用應該用 RAIDZ?
issachar 發表於 2016-10-28 16:53


RAIDZ2 要 6 隻碟
1. always 0% waste "overhead" space in ZFS allocation method e.g. "default 128K recordsize" or 1M recordsize   same case for  6,18 disc raidz2;     same case for 5,9,17 disc RAIDz1

2. 2 disk for checksum in raidz2, and it can protect many data disc, and 4 disc is the "min" storage space efficiency   considered the "party cost", remain is (4/6) 67% usable;   you can have 3 disc raidz2 by the way, but only (1/3) 33% space usable;   another option is go to 18 disk raidz2  (16/18) ~88% usable  <in 16 sector per block>

3. these 2 recommendations usually fit small installation like for a 8 ports internal hba card with remain a few ports for read cache / write cache "slog" to improve zfs performance

4. for 6 disc setup, it sounds better protection for "1x 6-disc radiz2" then "2x 3-disc raidz1" in big multi-tera byte hdd, although the IOPS is lower

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