On Fri, 9 Oct 2009, Derek Anderson wrote:
I created a NFS filesystem for vmware by using : zfs create
SSD/vmware . I had to set permissoins for Vmware anon=0, but thats
it. Below is what zpool iostat reads:
File copy 10Gbe to SSD -> 40M max
My clients here do better than that over gigabit ethernet if the file
is a large file. If by 'file' you mean directories of many small
files, then there are likely other factors at work.
Top shows not matter what I always have 2.5 G free and every other
test says the same thing. Can anyone tell me why this is seems to
be slow? Does 90M mean MegaBytes or MegaBits?
The units are megabytes.
It seems that many of these SSD products (e.g. Samsung SSDs) are
over-specified and the transfer rate specified is the "burst" rate
rather than the average continuous write rate. They also often have
limited buffering and command queing capability. After the device has
been used for a while, it needs to start erasing large blocks before
it can write blocks, which increases write latencies. Even though you
are using a SSD, ZFS is going to tell the device to sync its write
cache due to NFS synchronous writes.
I suggest that you try adjusting this zfs tunable in /etc/system
* Set device I/O maximum concurrency
*
http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Device_I.2FO_Queue_Size_.28I.2FO_Concurrency.29
set zfs:zfs_vdev_max_pending = 1
The default is 32. Since SSDs don't have heads or rotating media,
there is likely less benefit to queuing up a bunch of requests. If
this helps, try increasing the value until performance drops off.
Also, check the system log file for any messages involving bus resets
or other problems.
Lastly, you should use a network benchmark tool to verify that you
really are getting something close to 10Gbits of bandwidth. It is
quite possible that you have a broken network.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
