On Sat Dec 22, 2012, you wrote:
> On Fri Dec 21, 2012, Thomas Fjellstrom wrote:
> > I'm setting up a new nas box (7x2TB on a IBM M1015 8 port sas card
> > flashed to 9211IT mode) and was thinking about adding an SSD cache to
> > it. I've been following bcache's development, but it seems to have
> > stalled a bit.
> >
> > I've got a 240G Samsung 470/810 that I'd like to use for this.
> >
> > Also I was wondering if anyone has any tips on the best (or their
> > preferred) way to set up a "big" raid6 array with a single filesystem.
> > I'm probably going to stick with XFS, but I'm not married to it, if
> > there's something better for a big media (audio, video, disk images,
> > backups, etc) volume I'd love to hear about it.
>
> So my array has finally finished resyncing, and I've run a simple iozone
> test on it formated with xfs, and I'm seeing some somewhat low write
> results:
>
> moose@mrbig:/mnt/mrbig/data/test$ iozone -a -s 32G -r 8M
> random random
> bkwd record stride
> KB reclen write rewrite read reread read write
> read rewrite read fwrite frewrite fread freread
> 33554432 8192 212507 210382 630327 630852 372807 161710
> 388319 4922757 617347 210642 217122 717279 716150
>
> Is this normal for a 7 disk (2TB seagate barracudas) raid array on a pcie
> x8 sas controller?
>
> I was thinking it might be alignment issues, but there are no partitions on
> the disks, and xfs seems to have correctly set up the sunit and swidth
> settings (128/640 for a 7 disk raid6). While 200MB/s is probably more than
> I need day to day, I'd like to make sure it is set up properly.
So I've retested the array without bcache in th way, and my write speeds are
still a fraction of the read speeds. Is this normal for a setup like mine?
The iozone results are a bit odd as well, I'm seeing the write speeds get
worse as the record size goes up. To compare with the bcache result above:
random random
bkwd record stride
KB reclen write rewrite read reread read write
read rewrite read fwrite frewrite fread freread
33554432 8192 177919 167524 632030 629077 371602 115228
384030 4934570 618061 161562 176033 708542 709788
I'm pretty sure the bare results I got before I tested the bcache setup were
better than this, a little over 200MB/s. But with the current kernel, these
are the numbers I'm getting.
Specs:
Intel Core i3-2120
16GB 1333MHZ DDR3 ECC
30GB Vertex 1 SSD for /
IBM M1015 flashed with the LSI 9211-8i IT firmware
7x2TB Seagate Baracuda HDDs in raid6 unpartitioned and formatted with XFS
This system is currently dedicated to nothing but NAS duties. Later on I might
get it doing other things, but right now, its actually doing nothing but
running a RAID6 array that I haven't started using yet, so there shouldn't be
too much getting in the way of the iozone tests.
--
Thomas Fjellstrom
thomas@xxxxxxxxxxxxx
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