On Sat, Jan 03, 2004 at 11:20:24PM +0100, Jan Minar wrote:
> On Sat, Jan 03, 2004 at 04:52:06PM -0500, Andy Firman wrote:
> > Do the physical drives and partitions have to be EXACTLY the
> > same for RAID 1 to work properly or will the following
> > layouts of my drives be sufficient?
>
> Briefly: no: Linux kernel software RAID won't mess with the disk's
> internals.
>
> <snip />
> > Disk Drive: /dev/hda
> > Size: 40000000000 bytes
> > Heads: 255 Sectors per Track: 63 Cylinders: 4863
> <snip />
> > Disk Drive: /dev/hdd
> > Size: 40020664320 bytes
> > Heads: 16 Sectors per Track: 63 Cylinders: 77545
> <snip />
>
> You can see you have two completely different disks. You might use
> hdparm(8) to see what the disk report themselves to be, really.
This is interesting. I took hdd and put it on hdb and did this:
dd if=/dev/hda of=/dev/hdb
which took over 5 hours as I went to bed. It was done this am.
Now look what cfdisk reports:
Disk Drive: /dev/hda
Size: 40000000000 bytes
Heads: 255 Sectors per Track: 63 Cylinders: 4863
Disk Drive: /dev/hdb
Size: 40020664320 bytes
Heads: 255 Sectors per Track: 63 Cylinders: 4865
remember that /dev/hdb is the same drive as /dev/hdd (I just moved
the drive to do the dd command)
So by doing dd, the hdb(hdd) disk now has 255 heads instead of just
16 and it's cylinders went from 77545 down to 4865.
So now my completely different disk's are not so different...no?
And here is what hdparm says about both drives:
debian:~# hdparm -i /dev/hda
/dev/hda:
Model=WDC WD400BB-75DEA0, FwRev=05.03E05, SerialNo=WD-WMAD19841353
Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=40
BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=78125000
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive Supports : Reserved : ATA-1 ATA-2 ATA-3 ATA-4 ATA-5
debian:~# hdparm -i /dev/hdb
/dev/hdb:
Model=WDC WD400BB-00GFA0, FwRev=09.01B09, SerialNo=WD-WCAKA1203407
Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=40
BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=78165360
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive Supports : Reserved : ATA-1 ATA-2 ATA-3 ATA-4 ATA-5
I guess my question is what really controls the CHS layout of a disk?
(Nate mentioned firmware in a recent post.)
The dd in this command obviously changed the hdb drive's CHS layout.
-Andy
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