Richard,
RAID0 is considered to have a worse performance than JBOD with 2 disks
with one cache directory per disk. Since you mentioned that you have
to stick with RAID0 all you can do is optimize the RAID0 usage.
Only one cache directory per disk is recommended while you have 4 cache
directories on one file system. Consider dropping 2 COSS cache directories
so that you have 1 COSS and 1 AUFS.
Kinkie and I rewrote the RAID for Squid section of the FAQ and
it includes more details about price, performance and reliability trade-offs.
You will find that Software RAID5 is the slowest option.
-Marcus
Richard Wall wrote:
On Tue, Mar 25, 2008 at 1:23 PM, Marcus Kool
<marcus.kool@xxxxxxxxxxxxxxx> wrote:
I wish that the wiki for RIAD is rewritten.
Companies depend on internet access and a working Squid proxy
and therefore the advocated "no problem if a single disk fails"
is not from today's reality.
One should also consider the difference between
simple RAID and extremely advanced RAID disk systems
Recently I've spent a fair bit of time benchmarking a Squid system
whose COSS and AUFS storage (10GB total) + access logging are on a
RAID0 array of two consumer grade SATA disks. For various reasons, I'm
stuck with RAID0 for now, but I thought you might be interested to
hear that the box performs pretty well.
The box can handle a 600 - 700 Req/Sec Polygraph polymix-4 benchmark with a
~40% document hit ratio.
usage
Doubling the total storage to 20GB, increased the doc hit ratio to
55%, but hit response times began to increase noticably during the top
phases.
CPU was about 5% idle during the top phases. Logs were being rotated
and compressed every five minutes. CPU usage never
Some initial experiments suggest that removing RAID doesn't
particularly improve performance, but I intend to do a more thorough
set of benchmarks soon.
I'm not sure how relevant this is to your discussion. I don't know how
RAID0 performance is expected to compare to RAID5.
I'll post here if and when I do more benchmarking without RAID.
-RichardW.
== Spec ==
CPU: Intel(R) Celeron(R) CPU 2.53GHz
RAM: 3GB
Disks: 2 x Seagate Barracuda 160GB
Squid: 2.6.STABLE17
Linux Kernel: 2.6.23.8
FS: reiserfs
== Squid Conf (extract) ==
# NETWORK OPTIONS
http_port 800 transparent
# MEMORY CACHE OPTIONS
cache_mem 152 MB
maximum_object_size_in_memory 50 KB
# DISK CACHE OPTIONS
cache_replacement_policy lru
# TOTAL AVAILABLE STORAGE: 272445 MB
# MEMORY STORAGE LIMIT: 46694 MB
# CONFIGURED STORAGE LIMIT: 10000 MB
cache_dir coss /squid_data/squid/coss0 2000 max-size=16000
cache_swap_log /squid_data/squid/%s
cache_dir coss /squid_data/squid/coss1 2000 max-size=16000
cache_swap_log /squid_data/squid/%s
cache_dir coss /squid_data/squid/coss2 2000 max-size=16000
cache_swap_log /squid_data/squid/%s
cache_dir aufs /squid_data/squid 4000 16 256
max_open_disk_fds 0
maximum_object_size 20000 KB
# LOGFILE OPTIONS
debug_options ALL,1
buffered_logs on
logfile_rotate 10
# MISCELLANEOUS
memory_pools_limit 10 MB
memory_pools off
cachemgr_passwd none all
client_db off
