HIGH Latency Datastore

[pooly]

Hi

I Have a HP DL180 G6 With raid controller P410 With Installed esxi 4.1.0 Build 260247.

My problem is Very High Latency In dataStore. ( Write Latency average Is 200-250 ) and then Very Slow Installation Guest OS, take many Hours !!!

Please Help Me

I have 9 VM.

Attached Picture is My latency graph when win2008 r2 going to install.

Sorry For Poor English.

Sincerely Yours

[rickardnobel]

How is the RAID configuration setup? Do you have battery backed write cache? It might be that the write cache is disabled and causes this very high latencies.

[pooly]

Thank For Your Answer.

My raid Setup IS RAID1.

what is That ? ( battery backed write cache ).

and That Do Which Work ?

How can i Check Write Cache so that not be diabled ?

Sincerely Yours

[rickardnobel]

The write cache is memory on the RAID controller which could greatly increase your write performance. However, since the risk of data loss if there is a power failure the controller card wants a local battery which could hold the unwritten IOs until power returns.

You would have to check the specifications for this specific server and the version of the RAID controller to see which features it supports. When the server is rebooting you could enter the Controller "BIOS" and see which options you can change. There could also be vendor CDs, like HP Smartstart, which you could boot the server and perhaps get more visibility into the controller setup.

[LogitComputer]

Hello,

As the poster above, you MUST have a BBWC or FBWC with the HP SmartArray Controllers for a good ESXi Datastore Performance.

I tested this in my lab with couple of configurations, trust me...

There is a "256MB Only" Kit wich can be purchased, but without BBWC, the Datastore Performance is still very slow (in my case around 3MB/sec write speed).

Now I have > 220MB/sec on a RAID5 with 7200rpm SAS or > 400MB/sec on a RAID5 with 15'000rpm SAS.

Buy a 512MB BBWC (Battery Backed Write Cache) or FBWC (Flash Backed Write Cache) for the P410.

If you have enought money you can buy 1GB FBWC, but I didn't test this because 512MB is enough for me and my clients.

HPs description: http://h18000.www1.hp.com/products/servers/proliantstorage/arraycontrollers/smartarrayp410/index.htm...

Furthermore, the DL180 is a supported Server. Download and install (if not already done by HPs Customized ESXi Image) the HP ESXi Offline Bundle, description: http://h18000.www1.hp.com/products/servers/software/vmware-esxi/offline_bundle.html

Regards,

Josip

[a_p_]

As mentioned by the other posters, write cache (BBWC/FBWC) is the key to datastore performance.

Without write cache the controller operates in write-through mode and each write operation will only be committed after the data has been written to the disk (which slows down the system). With write cache the controller operates in write-back mode. This way the ontroller commits the write operation immediately after buffering the data in the cache and writes the data to the disk later, without the OS having to wait for it.

André

[LogitComputer]

And this is the technically correct explanation WHY it is so slow

With HP SA, you can override from writhe-through to write-back even if there is no BBWC enabled in the HP SA Firmware (Press F8 when the RAID Firmware comes to screen).

In my opinion it is not the way how a productive server should be set up (means without BBWC).

[BharatR]

Hi

Reboot the Server with the HP SmartStart CD Latest Version 8.70 and after accepting the License Agreement

u can find Maintenance option in that there will be Array Configuration Utility

Go to Array Configuration Utility->select the Controller Card->click on More Information

it will show the Battery(BBWC) Status and the Read and Write performance should be 50% equal

check and confirm the same

[ccinatl]

you could just be pushing too many iops with 9 machines.  how many iops are you hitting?

if only raid 1, you're looking at a max from 200 (sata) - 375 (15k) iops - half that for write.