Resending this as I never saw it show up on the list (sent out
yesterday) (while other the messages came back in under 15 minutes
Have started to use RAID on a few of my disks and forgot about the
xfs 'su*sw' and 'sunit*swidth' options.
From what I get in reading the manpage, 'su' is used with 'sw' and
'sunit' is used with 'swidth'?
The RAID controller in one of my machines uses a "strip element" size,
expressed in bytes, allowed values seem to be limited to powers
of 512*2^*[1..11] (512B up to 1MB) (though as previously noticed, although
xfs's manpages claims to allow one expresses sizes with the unit 'm', it
only permits .25m (256k), I guess I never tried seeing if the command line
would take floating point ;^) ).
I believe 'su' would be set to the 'strip element size' (in k or m).
Then, for RAID 1 (mirror) would 'sw'==1? Would setting the su/sw value
for a RAID 1 actually matter in any way? Ie, technically -- it would
fill in numbers for OS book-keeping, but wouldn't change anything in
terms of performance or layout, vs. 'physically' -- where it could change
disk layout or performance?
At RAID 0, I'd guess sw==2?
In RAID 5, would it be sw == #Disks-1? So even w/6 disks, it still only
uses 1 disk for parity and sw == 5?
I wonder what becomes a max-safe RAID 5 size? (or is the number of parity
disks a settable option with RAID 5?)