> My testing has shown some serious problems with the
> iSCSI implementation for OpenSolaris.
> 
> I setup a VMware vSphere 4 box with RAID 10
> direct-attached storage and 3 virtual machines:
> - OpenSolaris 2009.06 (snv_111b) running 64-bit
> - CentOS 5.3 x64 (ran yum update)
> - Ubuntu Server 9.04 x64 (ran apt-get upgrade)
> 
> I gave each virtual 2 GB of RAM, a 32 GB drive and
> setup a 16 GB iSCSI target on each (the two Linux vms
> used iSCSI Enterprise Target 0.4.16 with blockio).
> VMware Tools was installed on each. No tuning was
> done on any of the operating systems.
> 
> I ran two tests for write performance - one one the
> server itself and one from my Mac connected via
> Gigabit (mtu of 1500) iSCSI connection using
> globalSAN’s latest initiator.
> 
> Here’s what I used on the servers:
> time dd if=/dev/zero of=/root/testfile bs=1048576k
> count=4
> and the Mac OS with the iSCSI connected drive
> (formatted with GPT / Mac OS Extended journaled):
> time dd if=/dev/zero of=/Volumes/test/testfile
> bs=1048576k count=4
> 
> The results were very interesting (all calculations
> using 1 MB = 1,084,756 bytes)
> 
> For OpenSolaris, the local write performance averaged
> 86 MB/s. I turned on lzjb compression for rpool (zfs
> set compression=lzjb rpool) and it went up to 414
> MB/s since I’m writing zeros). The average
> performance via iSCSI was an abysmal 16 MB/s (even
> with compression turned on - with it off, 13 MB/s).
> 
> For CentOS (ext3), local write performance averaged
> 141 MB/s. iSCSI performance was 78 MB/s (almost as
> fast as local ZFS performance on the OpenSolaris
> server when compression was turned off).
> 
> Ubuntu Server (ext4) had 150 MB/s for the local
> write. iSCSI performance averaged 80 MB/s.
> 
> One of the main differences between the three virtual
> machines was that the iSCSI target on the Linux
> machines used partitions with no file system. On
> OpenSolaris, the iSCSI target created sits on top of
> ZFS. That creates a lot of overhead (although you do
> get some great features).
> 
> Since all the virtual machines were connected to the
> same switch (with the same MTU), had the same amount
> of RAM, used default configurations for the operating
> systems, and sat on the same RAID 10 storage, I’d say
> it was a pretty level playing field. 
> 
> While jumbo frames will help iSCSI performance, it
> won’t overcome inherit limitations of the iSCSI
> target’s implementation.

cross-posting with zfs discuss.
-- 
This message posted from opensolaris.org
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss

Reply via email to