Should I bother with a gvinum stripe when using a pair of SSDs?

[Jens Schweikhardt]

On Sat, Feb 16, 2013 at 04:44:06PM +0100, C. P. Ghost wrote:
# On Sat, Feb 16, 2013 at 3:47 PM, Jens Schweikhardt
# <schweikh at schweikhardt.net> wrote:
# > hello, world\n
# >
# > currently the only gvinum partition on my home system is a stripe for /home
# > across two Velociraptor HDDs. I'm thinking of replacing the HDDs with a
# > pair of SSDs. I was thinking of reducing complexity and in the migration
# > possibly no longer use gvinum at all--one less thing to configure and worry
# > about.
# >
# >  * Would gvinum striping bring any speed advantage with a pair of SSDs?
# >  * Or am I hitting other limits so that striping SSDs is a waste anyway?
# >  * Should I finally take the plunge and acquaint myself with ZFS?
# >
# > System has 4GB RAM in an ASUS P5Q3 Deluxe with SATA II. It appears to me
# > that SATA II with 300MB/s is maxed out by a single SSD and striping it
# > will not improve r/w throughput. Is my simplistic reasoning correct?
# 
# Jens,
# 
# as always it depends on what you're trying to achieve:
#   - max speed / lower latency?
#   - max storage?
#   - max redundancy?
#   - max run-time-to-data-loss?
# 
# Your choice of SSD probably means you'd like to reduce latency
# and maximize data throughput.

Exactly, when I started vith vinum many years ago in the magnetic HD
age, striping with vinum gave me almost factor 2 in r/w speed as
measured with dd. (I do backups regularly to other media, so data
loss protection is not my primary concern).

I realize that maximum SSD speeds as advertised by vendors and tests
(e.g. 520MB/s for contemporary top notch SSDs) may only be reached
under certain conditions far away from my normal usage, which is
re-building worlds and kernels and ports on a daily basis. So if for
my realworld working set a single SSD can deliver 300MB/s, striping
with vinum just might get me a factor 2 again to 600MB/s across
two SSDs. Then it would be worthwile to keep gvinum.

Does that make sense? My understanding of SSD and SATA capabilities
may however be completely dreamed up...


Regards,

	Jens
-- 
Jens Schweikhardt http://www.schweikhardt.net/
SIGSIG -- signature too long (core dumped)