[Gllug] OT: Replace old model WD Raptor with new within CentOS

t.clarke tim at seacon.co.uk
Thu May 27 04:14:58 UTC 2010

The last reply certainly makes sense to me!
Whilst not the same type of RAID,  we are using LSI SCSI controllers with
integrated mirroring and they work fine with different discs PROVIDING that
a) the 'primary' disc is not greater in size (by even 1 sector!) than the '
secondary' disc
b) the discs are the same scsi speed (both U160 or both U320)

In theory I am told, U160 and U320 will work together, but performance will
be probably hit horribly.

Physical seek time would seem irrelevant as the discs normally cache the
writes and return 'complete' to the controller before the physical write to
the platter is complete (unless the controller instructs otherwise!).
Reads, in the case of mirroring, are done from one or the other drive only.

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