Xsan working slow - 18Mb/s on Read and 100Mb/s on Write

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Xsan working slow - 18Mb/s on Read and 100Mb/s on Write
by Harry Grinling on Jun 11, 2005 at 6:27:55 am

Hi All,

We have an Xsan set up which is running slow when it is reading from the Xsan. We have just tested it with the AJA utility and it has a write speed of 100Mb/s and a read speed of 18Mb/s.

This is resulting in dropped frames when multiple systems are reading from the system or writing to the system.

The setup is as follows:

1 X 5.6Tb with Metadata on a RAID 1 volume on a seperate LUN and the data across the other lun is set to fill.
2 X G4 FCP clients
2 X G5 FCP clients
1 X QLogic 5200
2 X GB Switches
1 X Cluster node (MDC)
1 X Xserve with sharepoint acting as NAS head and (BMDC)

1.The metadata LUN is RAID 1
2. The metadata LUN is not on its own RAID controller, but we are only running DV here so should not effect it to much.
3. The RAID is fully populated with seven drives on each side (with a hot spare).
4. Both sides of the Xserve RAID are RAID Level 5
5. The Metadata network is a separate physical network from the WAN network
6. The metadata controllers (MDCs) are set to connect to the Xsan network using the interface that is reserved for metatdata
7. All the Network Services interface are the highest priority in our Port Configurations
8. The MDCs is dedicated to Xsan.
9. The Xsan client and MDC are not resolving their Network Services interface to a Fully Qualified Domain Name.
10. The Apple Fibre Channel Cards are installed in the correct slot
11. All Fibre Channel Interfaces

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Re: Xsan working slow - 18Mb/s on Read and 100Mb/s on Write
by Peter Wiggins on Jun 11, 2005 at 6:54:21 pm

Harry,

Have you read the excellent advice given in the thread below re 5200?

http://www.creativecow.net/forum/view_thread.php?threadid=837151&forumid=18...

Peter

http://www.peterwiggins.com

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Re: Xsan working slow - 18Mb/s on Read and 100Mb/s on Write
by Harry Grinling on Jun 13, 2005 at 10:37:35 pm

Peter,

Thanks for the feedback on that, we updated the firmware and we set the initiators to enabled for the streamGuard and it made no difference.

Looking at the config again I can see that the RAID unit is set to fill. The Luns are setup as folllows:

Disk 1 and 2 = Metadata RAID 1
Disk 3 to 6 = Storage pool 1
Disk 7 = Hot Spare

Other side of RAID is set to:

Disk 1 to 6 = Storage Pool 2
Disk 7 = Hot Spare

Storage Pool 1 and 2 are not striped across the two controllers.

Does any one have any experiance of this configeration and what the expected through put would be for a system that is running this config?

Thanks

Harry.

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Re: Xsan working slow - 18Mb/s on Read and 100Mb/s on Write
by Matt Geller on Jun 18, 2005 at 1:40:47 am

Harry...

Oy.

Your configuration is yielding probably the worst performance for a fully populated Xserve RAID. In any storage environment, the most disks mechanisms working together will yield the greatest performance.

Setting the allocation of the volume to "Fill" actually instructs the Xsan software to fill the first Storage Pool until it is completely full before it then moves on to the next Storage Pool, etc. In your current config, your first Storage Pool, consisting of 4 drives, is the only storage that will be used until it is full. Only then would it even start to hit the second storage pool of 6 drives.

There's a reason that the default setting is "Round Robin," since it hits each Storage Pool with equal amounts of data. Unfortunately, changing this setting in the volume will need a re-initializing of it. But we're not done yet.

Your allocation of Disks 1 & 2 are well done. But then, you'd do much better setting Disks 3-7 as a RAID 5, and then Disks 8-12 as another RAID 5 (on the other side), and finally setting Disks 13-14 as a RAID 0 for Miscellaneous non-critical storage. This way, you can pool the two 5-drive RAID5 LUNs into a single Storage Pool. Ten drives working together will yield far greater performance that you are currently getting. Further, setting simple root-level folders with affinities for the RAID 5 based Storage Pool and the RAID 0 based Storage Pool respectively will ensure that data gets routed to the correct mixture of performance and redundancy.

So, if you can manage to start over, reallocate your LUNS in the above config, and make sure to create the new volume with Round Robin allocation.

Lastly, if you're worried about losing your Hot Spare drives, just remember that with one Xserve RAID in an Xsan, it's not prudent to lose two drives' performance for the sake of convenient redundancy.

Matt Geller
THETECHTHERAPIST
Full Service Consulting & Integration | Proactive & Reactive Maintenance
Xsan Integration Specialists | Certified Trainer for Apple Pro Apps & Boris Products
http://thetechtherapist.com

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Re: Xsan working slow - 18Mb/s on Read and 100Mb/s on Write
by Harry Grinling on Jun 18, 2005 at 8:11:53 am

Hi Matt,

Thanks for the reply.

This is where we had got to as well and we are backing up all the information and doing a re config over the weekend.

Makes perfect sense, I think our integrator was confused about the way that XSAN creates the stripe itself.

I will let you know how it goes.

Harry.

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