[Samba] Mirrored samba servers.

Greg Freemyer greg.freemyer at gmail.com
Wed May 4 18:37:27 GMT 2005

On 5/4/05, Thomas Widhalm wrote:
> > The problem is he has an ata system.  If we went with a raid, we would
> > want a 0,1 raid. striped with mirroring and I can't find a raid ata card
> > to do that.
> I don't know, what performance is needed by your client, but you could
> use 4 ATA drives and build one RAID5 out of them with the Linux
> Software- Raid feature. (Remember the / has to be on a Raid 1 Partition
> in that case, because Linux can't boot from Raid 5)

I missed the beginning of this, but if the question is what kind of
hardware ATA raid controller will support Raid 10  (striped sets of
mirrored disks), then I would look into the 3ware cards.

I've recently heard some complaints about the speed, but I don't know
how valid those complaints are and I have seen a lot of high
performance servers built around the 3ware cards with 2.4 kernels.

for traditional ATA drives, see:  http://www.3ware.com/products/parallel_ata.asp

for SATA drives, see:  http://www.3ware.com/products/serial_ata.asp

FYI: I don't think there is anything inherently wrong with Linux MD
(software raid), but the IDE bus only allows the master OR the slave
to be active at any one time.  This means that a seek command that
takes 10 msecs to complete causes the alternate drive to waste 10
msecs.  High performance IDE systems really should be designed around
master only configs.  The 3ware cards indeed only support drives
configured as master, so if you buy the 12 -port card and put 12
drives on it you would have 12 drives configured as master.

FYI2: Even with just 2 masters, most dual-channel motherboard ide
controllers I have tested cannot get 2x performance from the 2 drives.
 As a simple test boot a linux boot CD and do a raw dd between two
scratch drives and calculate the speed.

ie. time dd bs=4k count=1000000 if=/dev/hda of=/dev/hdc

That will copy 4 GB.  A good setup should be able to do that in 2
minutes or so.  I have seem machines that take 5 or more minutes.

Greg Freemyer
The Norcross Group
Forensics for the 21st Century

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