On Wed, 28 Feb 2007, dean gaudet wrote:
On Mon, 26 Feb 2007, Neil Brown wrote:
On Sunday February 25, jpiszcz@xxxxxxxxxxxxxxx wrote:
I believe Neil stated that using bitmaps does incur a 10% performance
penalty. If one's box never (or rarely) crashes, is a bitmap needed?
I think I said it "can" incur such a penalty. The actual cost is very
dependant on work-load.
i did a crude benchmark recently... to get some data for a common setup
i use (external journals and bitmaps on raid1, xfs fs on raid5).
emphasis on "crude":
time sh -c 'tar xf /var/tmp/linux-2.6.20.tar; sync'
xfs journal raid5 bitmap times
internal none 0.18s user 2.14s system 2% cpu 1:27.95 total
internal internal 0.16s user 2.16s system 1% cpu 2:01.12 total
raid1 none 0.07s user 2.02s system 2% cpu 1:20.62 total
raid1 internal 0.14s user 2.01s system 1% cpu 1:55.18 total
raid1 raid1 0.14s user 2.03s system 2% cpu 1:20.61 total
raid5:
- 4x seagate 7200.10 400GB on marvell MV88SX6081
- mdadm --create --level=5 --raid-devices=4 /dev/md4 /dev/sd[abcd]1
raid1:
- 2x maxtor 6Y200P0 on 3ware 7504
- two 128MiB partitions starting at cyl 1
- mdadm --create --level=1 --raid-disks=2 --auto=yes --assume-clean /dev/md1 /dev/sd[fg]1
- mdadm --create --level=1 --raid-disks=2 --auto=yes --assume-clean /dev/md2 /dev/sd[fg]2
- md1 is used for external xfs journal
- md2 has an ext3 filesystem for the external md4 bitmap
xfs:
- mkfs.xfs issued before each run using the defaults (aside from -l logdev=/dev/md1)
- mount -o noatime,nodiratime[,logdev=/dev/md1]
system:
- dual opteron 848 (2.2ghz), 8GiB ddr 266
- tyan s2882
- 2.6.20
-dean
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
I like your crude benchmark, it works well. I have not tested with a
bitmap, but it does not seem worth it to use those.
Here are my results (for disk speed/purposes only):
All FS are XFS with similar mount options as yours.
Raid1 Dual 74GB Raptor (older models, no NCQ) [no bitmap]
# time sh -c 'tar xf linux-2.6.20.tar; sync'
real 0m40.226s
user 0m0.200s
sys 0m1.515s
Raid5 Quad 150 Raptor (NCQ) [no bitmap]
# time sh -c 'tar xf linux-2.6.20.tar; sync'
real 0m21.721s
user 0m0.174s
sys 0m1.541s
Raid5 Six 400GB Sata Drives (some NCQ, some not) [no bitmap]
# time sh -c 'tar xf linux-2.6.20.tar; sync'
real 1m7.322s
user 0m0.194s
sys 0m1.492s
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
