Wilkinson, Alex wrote:
0n Thu, Apr 30, 2009 at 11:11:55AM -0500, Bob Friesenhahn wrote:
>On Thu, 30 Apr 2009, Wilkinson, Alex wrote:
>>
>> I currently have a single 17TB MetaLUN that i am about to present to an
>> OpenSolaris initiator and it will obviously be ZFS. However, I am
constantly
>> reading that presenting a JBOD and using ZFS to manage the RAID is best
>> practice ? Im not really sure why ? And isn't that a waste of a high
performing
>> RAID array (EMC) ?
>
>The JBOD "advantage" is that then ZFS can schedule I/O for the disks
>and there is less chance of an unrecoverable pool since ZFS is assured
>to lay out redundant data on redundant hardware and ZFS uses more
>robust error detection than the firmware on any array. When using
>mirrors there is considerable advantage since writes and reads can be
>concurrent.
>
>That said, your EMC hardware likely offers much nicer interfaces for
>indicating and replacing bad disk drives. With the ZFS JBOD approach
>you have to back-track from what ZFS tells you (a Solaris device ID)
>and figure out which physical drive is not behaving correctly. EMC
>tech support may not be very helpful if ZFS says there is something
>wrong but the raid array says there is not. Sometimes there is value
>with taking advantage of what you paid for.
So forget ZFS and use UFS ? Or use UFS with a ZVOL ? Or Just use Vx{VM,FS} ?
It kinda sux that you get no benefit from using such a killer volume manager
+ filesystem with an EMC array :(
-aW
Besides the volume management aspects of ZFS and self healing etc, you
still get other benefits
by virtue of using ZFS. Depending on *your* requirements, they can be
arguably more beneficial,
if you are happy with the reliability of your underlying storage.
Specifically I am talking of ZFS snapshots, rollbacks, cloning, clone
promotion, file system quotas, multiple
block copies, compression, (encryption soon) etc etc.
I have use snapshots, rollbacks and cloning quite successfully in
complex upgrades of systems with multiple
packages and complex dependencies.
Case in point was a Blackboard Upgrade which had two servers. Both with
ZFS file systems. One for
Blackboard and one for Oracle. The upgrade involved going through 3
versions of
Oracle and 4 versions of blackboard where the process had potentially
many places to go wrong. At every
point of the way we performed a snapshot on both Oracle and Blackboard
to allow us to
rollback any particular part that we got wrong. This saved us an
immense amount of time and
money and is a good real world example of where this side of ZFS has
been extremely helpful.
In the Oracle side this was infinitely faster than having to rollback
the database itself. BB had some very large
tables!
Of course to take maximum advantage of ZFS in full, then as everyone has
mentioned it is a good idea
to let ZFS manage the underlying raw disks if possible.
IMPORTANT: This email remains the property of the Australian Defence
Organisation and is subject to the jurisdiction of section 70 of the CRIMES ACT
1914. If you have received this email in error, you are requested to contact
the sender and delete the email.
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
