Re: Useful benchmarking tools for RAID

[michael@xxxxxxxxx]

Quoting Bryan Mark Mesich <bmesich@xxxxxxxxxxxxxxxxxxxxxxxxxx>:

> Good afternoon,
>
> I've been sitting back quietly reading posts over the past few months
> regarding RAID performance.  My ultimate goal is to increase the
> performance of our IMAP mail servers that have storage on-top RAID 5.
> During peek times of the day, a single IMAP box might have 500+ imapd
> processes running simultaneously.  As a result, the load increases as
> does the users blood pressure.
>
> I'm currently testing with the following:
>
> Intel SE7520BD2 motherboard
> (2) 3Ware PCI-E 9550SX 8 port SATA card
> 1 GB of memory
> (2) Core2Duo 3.0GHz
> (16) Segate 750GB Barracuda ES drives
> RHEL 5.1 server (stock 2.6.18)
>
> I've setup 3 RAID5 arrays arranged in a 3+1 layout.  I created them with
> different chunk sizes (64k, 128k, and 256k) for testing purposes.
> Write-caching has been disabled (no battery) on the 3Ware cards and I'm
> using ext3 as my filesystem.  When creating the filesystems, I used
> sensible stride sizes and disabled directory indexing.
>
> I ran bonnie 1.4 on 2 of the filesystems with the following results:
>
> ### Chunk size = 64k
> ./Bonnie -d /mnt/64/ -s 1024 -y -u -o_direct
>
> MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
> 1*1024 59185 50.9 21849  7.5 14490  5.0 16377 24.1212812 25.3 267.8  1.5
>
> ### Chunk size = 256k
> ./Bonnie -d /mnt/256/ -s 1024 -y -u -o_direct
>
> MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
> 1*1024 47650 40.6 22561  6.8 19019  6.9 16872 22.2209770 23.7 267.2  1.5

[snip]

> With this said, has anyone ever tried tuning a RAID5 array to a busy
> mail server (or similar application)?  An ever better question would be
> how a person can go about benchmarking different storage configurations
> that can be applied to a specific application.  At this point, I'm not
> sure which benchmarking tool(s) would serve useful in this situation and
> how that testing should be conducted.  Should I measure throughput or
> smiling email users :)

Hello,

I'm unfamiliar with the term 3+1 raid layout with 3 Raid 5 arrays. Can  
you be more specific, just curious.  :)

I've always found that raid 5 arrays show better performance on arrays  
with 6 or more disks. If this can't be achieved than a raid 10 might  
be more suited. Of course so many factors come into play.
If raid 5 is your only option, than perhaps try with an array with  
more devices.

You can try to get bonnie to benchmark many small files. Not sure how  
real world this is or not.

# bonnie++ -u root -f -s 0 -n 100:64000:0:128

I think this means 100x1024 files : ranging from 64K to : 0K : in 128  
directories. (or something like that)
Don't forget about some of the mount options for ext3 to speed things up like
 -o noatime,data=writeback
of course, these remove features that might be important to you.

Cheers,
Mike



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