[zfs-discuss] About Raid XOR write question
ruben at vfn-nrw.de
Mon May 16 05:46:03 EDT 2016
ZFS does bot read any parity data without issues with the actual one. Therefore it's important to scrub a pool once in a while.
So a raidz is all time faster than a raid5 because on a raidz one disk more is able to perform useful operations m.
> Am 16.05.2016 um 10:09 schrieb Homer Li via zfs-discuss <zfs-discuss at list.zfsonlinux.org>:
> A lot documents said "Raid penalty for write operation would be 4 (why 4 ? )
> 1.Read existing data
> 2.Read parity
> 3.Write new data
> 4.Write new parity
> For example, there are 5 drivers (4 data 4 drivers + 1 parity 1 drivers).
> My question:
> 1. Why not read/write existing data not contains parity data, if first read/write operation contain it , Does it mean reduce once read/write operation ?
> Why split 2 operations to 4 operations ?
> 2. Does raidz write new or modify a data need 4 step ? any help in copy on write ?
> Many thanks : )
> I hope my questions are clear
> sorry about my poor English
> Best Regards
> Homer Li
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> zfs-discuss at list.zfsonlinux.org
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