good practice to use flexflash, or not?

Answered Question

Hello!


I have a C220M3 on which I plan to install some Cisco UC Applications.


Now I was wondering, is it concidered good practice to install the Hypervisor on that Flexflash card?

Or is it better to install it on the DAS?


I only have one Flexflash card. Should I use this only if I have 2, or should I still go ahead and install the HV there?


What are the Up/Downsides?


I would really appreciate some advice here!


Thank you!

Correct Answer by smcquerr about 3 years 11 months ago

The user space (HV Partition) on the FlexFlash drives are intended for customers to use as an alternative boot device.  It is ideally suited for the ESXi hypervisor.   FlexFlash has proven to be stable and reliable, but like any technology there is the potential for issues.


The upside is cost benfit to the customers. 


Most customers want to take advantage of the mobility of virtualized servers using VMotion.  This requires a shared datastore.  For this reason customers often use a minimal Hard Drive configuration for boot purposes.  The VMWare Hardware Compatibility List requires specific controllers to be used with the software.  Because of this customers would be forced to use one of the hardware RAID controller options with the C-Series server.  They will also often choose a pair of hard drives for redundancy.


WMWare supports USB boot for ESXi, but the problem there is redundancy.  If you loose the USB stick you have nothing backing it up.  In version 1.5.1 of CIMC Cisco introduced mirroring (RAID) capabilities of the hypervisor partition between 2 cards.  There is no need for additional hardware outside of the FlexFlash controller which is integrated on all systems that support FlexFlash and a pair of SD cards ordered from Cisco.  This reduces the cost to the customer greatly and provides redundancy between the boot devices.


When using FlexFlash you are essentially booting ESXi from USB as far as the system and OS are concerned.  The most notable "downside" is that the VMWare installer will put the scratch partition on the local RAMdisk.  This is not good practice and it some manual configuration is required to configure a persistent scratch location.


The following VMWare Blog provides a good overview of booting from a USB (or SD) vs. Local Drives.


http://blogs.vmware.com/vsphere/2011/09/booting-esxi-off-usbsd.html



Hopefully this provides the type of information you need.  If you have additional question please let us know.


Steve McQuerry

UCS - Technical Marketing

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Keny Perez Mon, 08/26/2013 - 08:02
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Hi,


The Flexflash can easily hold the OS, you may use one or two SD cards.


In CIMC 1.4x the system only supports one card, from 1.5x and on, the system sees/supports both cards and then you can mirrored them, meaning this is not a requirement, but gives redundancy.


One thing that you want to know is that if you are running CIMC 1.5 and have one SD card, the system will show "RAID degraded" in the Flexflash section cause the system will be looking for 2 card mirrored (this mirroring can be done from the SCU {Server Configuration Utility})


THe SD card (Flexflash) has 4 partitions:


*HUU: Hardware Upgrade Utility (bootable ISO); 1.2-GB user read-only space

*SCU: Server Configuration Utility (bootable ISO); 3.2-GB user read-only space

*Drivers: Cisco Drivers ISO; 6.7-GB user read-only space

*HV: Hypervisor (bootable if made so by user); 3.2-GB user read-write space  <<< This is the space available for OS storage or it can also be seen as a normal USB drive for a VM, if desired.


Here you can find more valuable information:

http://www.cisco.com/en/US/solutions/collateral/ns340/ns517/ns224/ns944/white_paper_c11-718938.html



Let me know if you have any other doubt/question.



-Kenny

Hello!


Thanks for the Infos Keny.


I was more looking for an answer like "yeah, there is no problems with that CS Cards you should use it" or "No, I would stay away from it, it breaks a lot, its unreliable, it it much safer to install the os on the harddisks".


I don't really see the upside in using this flash drive instead of installing the os on the harddisks. But Cisco put it in there for a reason, right?

Correct Answer
smcquerr Wed, 08/28/2013 - 07:05
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  • Cisco Employee,

The user space (HV Partition) on the FlexFlash drives are intended for customers to use as an alternative boot device.  It is ideally suited for the ESXi hypervisor.   FlexFlash has proven to be stable and reliable, but like any technology there is the potential for issues.


The upside is cost benfit to the customers. 


Most customers want to take advantage of the mobility of virtualized servers using VMotion.  This requires a shared datastore.  For this reason customers often use a minimal Hard Drive configuration for boot purposes.  The VMWare Hardware Compatibility List requires specific controllers to be used with the software.  Because of this customers would be forced to use one of the hardware RAID controller options with the C-Series server.  They will also often choose a pair of hard drives for redundancy.


WMWare supports USB boot for ESXi, but the problem there is redundancy.  If you loose the USB stick you have nothing backing it up.  In version 1.5.1 of CIMC Cisco introduced mirroring (RAID) capabilities of the hypervisor partition between 2 cards.  There is no need for additional hardware outside of the FlexFlash controller which is integrated on all systems that support FlexFlash and a pair of SD cards ordered from Cisco.  This reduces the cost to the customer greatly and provides redundancy between the boot devices.


When using FlexFlash you are essentially booting ESXi from USB as far as the system and OS are concerned.  The most notable "downside" is that the VMWare installer will put the scratch partition on the local RAMdisk.  This is not good practice and it some manual configuration is required to configure a persistent scratch location.


The following VMWare Blog provides a good overview of booting from a USB (or SD) vs. Local Drives.


http://blogs.vmware.com/vsphere/2011/09/booting-esxi-off-usbsd.html



Hopefully this provides the type of information you need.  If you have additional question please let us know.


Steve McQuerry

UCS - Technical Marketing

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