Re: xen hosting providers recommendation.

[Greg Troxel <gdt%ir.bbn.com@localhost>]

Sorry, I know about r and was just typing too fast.
With r is indeed better, although slower than a real disk:

26928+0 records in
26928+0 records out
1764753408 bytes transferred in 107.378 secs (16434962 bytes/sec)

I just tried on my xen server at bbn (netbsd-4, i386, intel ICH7 mobo,
raid0 on a pair of seagate 750G SATA ST3750640NS), and got:

dom0 raw disk:

$ dd if=/dev/rraid0e of=/dev/null bs=64k
21436+0 records in
21436+0 records out
1404829696 bytes transferred in 17.607 secs (79788135 bytes/sec)

dom0 file (that backs the vnd for a domU)

$ dd if=foobar-wd1 of=/dev/null bs=64k
18428+0 records in
18428+0 records out
1207697408 bytes transferred in 30.316 secs (39836964 bytes/sec)

domU rxbd1e

$ dd if=/dev/rxbd1e of=/dev/null bs=64k
8987+0 records in
28987+0 records out
1899692032 bytes transferred in 40.461 secs (46951188 bytes/sec)

But, this is on a server with 10 domUs, almost all of which are sitting
there waiting for ssh or http requests and doing nothing.

16 MB/s isn't all that fast, but if one considers that's a fair-share of
a real disk among a lot of domUs, it's really pretty reasonable,
especially given how low the price is.

Are you using netbsd or linux as dom0, and is it raw partitions of
file-backed vnd?  I remember seeing something that indicated that NetBSD
did better at dom0 io.  (I realize there are a lot more issues in these
choices than vdisk performance.)