firewire disk spindown and other questions

[Hidetoshi Shimokawa]

At Wed, 13 Aug 2003 21:58:14 -0700 (PDT),
<kyriazis at meer.net> wrote:
> 
> Hello freebsd-firewire.
> 
> I am new to freebsd, and I am planning on changing my file
> server from linux to freebsd.
> 
> At the same time I would also like to move to firewire
> (from ide).  I don't have large bandwidth requirements, so I'm
> just assuming that I'm not going to get too much lower performance.
> 
> One basic question that I have is:  Is it possible to set an
> automatic spindown of my firewire drives?  I looked at the camcontrol
> manpage, but it doesn't say anything interesting.

freebsd-scsi should be the better place to ask this question.
There might be a mode page to control the automatic spindown but
I don't know.

> I am planning on setting up a raid-5 array (on firewire).  Are there
> any issues that I should be aware of??  Since I haven't tried
> firewire yet, and I am (slightly) worried about performance, I wonder
> if putting all drives on one chain will give me problems.  Would
> splitting drives over multiple firewire busses on the same card help
> any, or would I have to get multiple firewire cards to increase
> performance?  Note, this is a server machine, so I'll only be accessing
> data through 100Mbit ethernet via samba.

Because ports share the bandwidth of the bus, you need another
card(chip) to increase bandwidth. You can have only a bus by a chip
even if it has multiple ports.

I got about 32MB/s for a drive and 40 MB/s for two drives on a same bus
under sequential read.

Also, you could notice performance decreasing for buses which have
large number of nodes because of arbitration gap count increasing.

> Also, I was wondering if there are problems with the order firewire
> clients are brought up in the bus.  Will they come up as different
> each time I boot up?  Ie, if I have 2 disks, coming up as da0 and da1,
> will the same disk come up as da0?  Or will I have cases where one
> disk will come up as da0, then after a reboot the other disk will come
> up as ad0?  If that is in fact the case, will that cause problem with
> vinum identifying which disk is which, or will it work because of the
> labels vinum puts on the disks themselves?

If you plan to use FreeBSD-5.X, geom_vol_ffs kernel module would help.
It wires down the specific UFS partition to specific device name.

If you don't mind to apply a patch to sbp.c, you can hard-code
EUI64->target id mapping table into the source code.

The biggest problem for wire-down in SBP is that SBP has (64+48)bit 
identifier for the device but CAM cannot handle such big number.
So we have to map the device to small target numbers sequentially.

> Thank you!!
> 
>    --george

/\ Hidetoshi Shimokawa
\/  simokawa at sat.t.u-tokyo.ac.jp
PGP public key: http://www.sat.t.u-tokyo.ac.jp/~simokawa/pgp.html