Dell NAS Extremely Slow

I bought a low budget Dell NAS to be used to store exchange 2010 databases.  The disk are in RAID-5 and there are two NICs connected via iSCSI to the exchange servers, one NIC is connected to the LAN.. It take days to move a 56GB exchange database of archives mailboxes, day to move a 9gb exchange mailbox etc. How can I speed up that NAS!
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andreasSystem AdminCommented:
At first you should read this. If your RAID fails due to this issue you need to be sure you ALWAYS have recent working backups.

You should consider to use different RAID levels, e.g. 6, but RAID 6 is even slower, especially on low end NAS with weak CPUs.

Furthermore please give more specs on your NAS, if its really cheap one, you cannot expect to get high data rates on RAID5 as those NAS boxes use software RIAD and the internal CPU which needs to manage all the NAS operations also needs to calculate the RAID chunks and parity informations.
Also please give Specs. of your network, is the NAS and the exchange-Server connected via GBIT-Lan or is one of them just fast ethernet (100 MBit)?

Is the RAID5 creation already completed? if not wait until the RAID is fully initialized, the performance would be a lot better after creation process finished.

Scott GorcesterCTOCommented:
There are a number of things to consider. What is the speed of the drives? Are they SATA or SAS Drives? What other options for connectivity, What is the configuration of the iSCSI connections to the Exchange server and are they configured on the same IP subnet or different subnets. I typically con figure two seperate IP ranges for iSCSI so as to not cuz routing problems. Is the iSCSI network isolated from other networking. I prefer to have iSCSI switches dedicated to iSCSI rather than putting iSCSI on the production network or in a VLAN on the same hardware as the production network.

also how are you doing your copies, are you using a move command or taking the infomation store offline and copying the file.

masterofallAuthor Commented:

The NAS is  Dell PowerVault NX400, Entry Level, 8GB of RAM
H319 Raid Controller
4 x 1TB 7.2K RPM Near-Lin SAS 6Gops 3.5in Hot Plug in disk in RAID-5
2 x 1GB NIC plus 4 x 1Gb NIC = 6 Nics

The Exchange server and NAS are directed connected via 1GB NIC (No switch), Microsoft iSCSI target, displayed connection speed on the iSCSI NICs is 1GB, NAS drives appear as local drives to the exchange server.
IP addresses on the EXCHANGE/NAS iSCSI NICs are not the same subnet at the rest of the network.

The NAS and exchange server are also connected to the LAN via a 1 GB Cisco Catalyst switch.  The NAS is supposed to use this LAN NIC for Internet access.

We use the exchange management console to move dismounted databases or live mailboxes.

All databases are backed up daily. My equipment is new and I have seen a disk failure in a RAID-5 set in many years

I am going to replace the  RAID-5 NAS/7.2K drives by RAID-10 NAS/10K drives (10K not 15 K because the max size of 15K disks is 600Gb) but I need to be sure about the reason why the PowerVault NX400 is slow.
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masterofallAuthor Commented:
I meant that I am going to replace this NAS with RAID-5 NAS/7.2K drives by a new NAS with RAID-10 NAS/10K drives (10K not 15 K because the max size of 15K disks is 600Gb) but I need to be sure about the reason why this PowerVault NX400 is slow.  

I may reconfigure that NAS. Dell say that this PowerVault NX400  can only be configured as RAID-5 but the documentation says otherwise.
andreasSystem AdminCommented:
is the direct IP connection at its own IP subnet? OR is it same as the IPs net on the switch. if yes. give the direct link its own IP range. And then setup the exchange server to access to NAS via the 2nd direct links IP-Address.

If IPs are in the same subnet it will be very slow...

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masterofallAuthor Commented:
I did say that ' IP addresses on the EXCHANGE/NAS iSCSI NICs are not the same subnet at the rest of the network.'  

The Dell sales rep that sold me says that reason for the slow speed in the RAID-5 but its the best that he could have done within the budget. He also said that the NAS only support RAID-5 but that is not what the documentation that I posted above states. It states that RAID-5 is the default but others as available custom cofigurations.

The setup was done by Dell Professional Services and I assumed that they knew what they are doing but something is not quite right.
Scott GorcesterCTOCommented:
I agree that this is an entry level SAN with slow disks and the performance will not be as good as a high end system with faster drives.  That said I think your performance is slower than it should be. Maybe try just a simple file copy of one gigabite of data on different systems to see how a local disk copy compares to a copy to the san volumes.

I typically put 15K drives in sans and the more drives (i.e. spindles) the more throughput you will see. I don't think that removing 4ea 7.2k drives and replacing with 4ea 10k drives will not see a big change in speed (the IOPS CAN be calculated). Now moving from 4ea 7,2k to 10ea 10k drives will see an improvement in throughput.

RAID5 does have some overhead but its a common configuration for many SANS.

You said you have TWO iscsi nics connected to the exchange server correct? if so I would recommend those are on two different subnets i.e 10.1.1.x and 10.2.1.x, this will insure that you do not have routing problems.

Are all devices set up using jumbo frames?(switches ,NIC's)
Are all devices and NIC's set to auto only?
Since you are running a version of  M$ Windows Storage Server 2012 R2,you can download a utility like Iperf and test the speed between server and NAS.

My number one suspect is that PERC H310,it's a non caching RAID controller with horrendous write issues.

Get a H710,that's a real RAID card.
masterofallAuthor Commented:
Moosesupport, a) I plan replace the NAS not upgrade it.
b)The two iSCSI links are on the same subnet but different from the LAN subnet)
c) One of the iSCSI NICS are showing a very tiny  byte count, only 1 is carrying the load
d) The H310 is an entry level card. It does not appear to have a cache. see
e) Dell is going to run DPACK on it and try to figure out where is the bottleneck!
f) I will take a look at the NICs later.
c) One of the iSCSI NICS are showing a very tiny  byte count, only 1 is carrying the load

Unless they are set up to load balance  ,that's all you may see.
masterofallAuthor Commented:
Della asked me to use  DPACK to capture performance data. I will give an update ASAP.
masterofallAuthor Commented:
Dell DPACK showed the problem is latency on write to the RAID-5 set.
That's the controller.
No cache ,no performance.
Scott GorcesterCTOCommented:
I agree, also wonder if having two iscsi connections is causing even more trouble. If you're not using  a multipath configuration it may perform better with just one path.
Most folks just don't get that cheap RAID  controllers are just xor on a chip and pretty much suck on RAID 5.

 Battery backed cache allows for write-back mode,which significantly enhances the write performance of a RAID array.
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