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Difference between revisions of "Hardware"
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→Hardware RAID controllers
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* Sector size information is not necessarily passed correctly by hardware RAID on RAID 1 and cannot be passed correctly on RAID 5/6. Hardware RAID 1 is more likely to experience read-modify-write overhead from partial sector writes and Hardware RAID 5/6 will almost certainty suffer from partial stripe writes (i.e. the RAID write hole). Using ZFS with the disks directly will allow it to obtain the sector size information reported by the disks to avoid read-modify-write on sectors while ZFS avoids partial stripe writes on RAID-Z by desing from using copy-on-write. | * Sector size information is not necessarily passed correctly by hardware RAID on RAID 1 and cannot be passed correctly on RAID 5/6. Hardware RAID 1 is more likely to experience read-modify-write overhead from partial sector writes and Hardware RAID 5/6 will almost certainty suffer from partial stripe writes (i.e. the RAID write hole). Using ZFS with the disks directly will allow it to obtain the sector size information reported by the disks to avoid read-modify-write on sectors while ZFS avoids partial stripe writes on RAID-Z by desing from using copy-on-write. | ||
** There can be sector alignment problems on ZFS when a drive misreports its sector size. Such drives are typically NAND-flash based solid state drives and older SATA drives from the advanced format (4K sector size) transition before Windows XP EoL occurred. | ** There can be sector alignment problems on ZFS when a drive misreports its sector size. Such drives are typically NAND-flash based solid state drives and older SATA drives from the advanced format (4K sector size) transition before Windows XP EoL occurred. This can be [[Performance_tuning#Alignment_Shift_.28ashift.29 | manually corrected]] at vdev creation. | ||
** It is possible for the RAID header to cause misalignment of sector writes on RAID 1 by starting the array within a sector on an actual drive, such that manual correction of sector alignment at vdev creation does not solve the problem. | ** It is possible for the RAID header to cause misalignment of sector writes on RAID 1 by starting the array within a sector on an actual drive, such that manual correction of sector alignment at vdev creation does not solve the problem. | ||