Re: [Xen-users] Linux Fiber or iSCSI SAN

[Anastas Semenov <anastas.semenov@xxxxxxxxx>]

Hey Mark,

>>>  - 10 drives are are used for RAIDZ1 (2TB 3.5" WD Enterprise Black HDD)
>
>
> The problem I see with this is that you're absolutely killing your random
> I/O performance. In this configuration every 12 drive JBOD brick will
> perform random I/O about as well as a single hard drive.

There are choices to be made, as always capacity vs performance...
We are setting this cluster up for Hadoop, with large(r) files and a
lot of sequential reads..
I recognize that switching to striped 8+2 raidz2 groups would be much
better, and I've love to do it, as long as I can get the $$ for it..

> Also 10 drives is too much for RAIDZ1.

While 10 drive raidz1 is not most optimal, it is still pretty close to
recommended 4-8 drives.
Perhaps, we are better off going to raidz2.. This is still very much
in evaluation stage.. but so far, we've seen reasonable performance.
More testing required..

Check out this page on ZFS for Luste with Infiniband and 10GigE:
http://zfsonlinux.org/llnl-zfs-lustre.html

Anastas S
sysadmin++

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