thuang2
Contributor
Contributor

A few questions about VMware Flash Read Cache (vFRC)

Jump to solution

Hi,

1) There is a way to fake a VMFS datastore as SSD device. See instructions in the following link:

     http://tomverhaeg.nl/vmware-esxi/vmware-esxi-tag-a-device-as-local-and-ssd/

    

     1a) Can we fake a NFS datastore as a SSD device?

     1b) The partitions on the SSD device have to be empty in order for vFRC to work.

           There are two scenarios here: empty lun (with no VMFS filesystem) and VMFS LUN (with no data). Would both scenarios work for vFRC?

2) Can one SSD device be shared by multiple ESXi hosts?

3) Can multiple flash pools be created per ESXi host? If so, what's the maximum number of flash pools can be created per ESXi host?

4) Can a SSD device be used as a local disk?

0 Kudos
1 Solution

Accepted Solutions
admin
Immortal
Immortal

     1a) Can we fake a NFS datastore as a SSD device?  

>>NO

     1b) The partitions on the SSD device have to be empty in order for vFRC to work.

           There are two scenarios here: empty lun (with no VMFS filesystem) and VMFS LUN (with no data). Would both scenarios work for vFRC?

>> empty lun with no partitions is needed.. VMFS partitioned luns cannot be used because VFRC works with VFFS filesystem

2) Can one SSD device be shared by multiple ESXi hosts?

>>   not in vFRC context, normal VMFS datastore on SSD lun can be shared and used for  features like "swap to ssd"

3) Can multiple flash pools be created per ESXi host? If so, what's the maximum number of flash pools can be created per ESXi host?

>>  no, there can be only one pool which will be shared for all VMDK's enabled for using vFRC. as well as swap to SSD if configured.

4) Can a SSD device be used as a local disk?

>> claiming remote as local is possible. but not recommended and performance improvement is not guaranteed in that case with vFRC..

View solution in original post

0 Kudos
3 Replies
admin
Immortal
Immortal

     1a) Can we fake a NFS datastore as a SSD device?  

>>NO

     1b) The partitions on the SSD device have to be empty in order for vFRC to work.

           There are two scenarios here: empty lun (with no VMFS filesystem) and VMFS LUN (with no data). Would both scenarios work for vFRC?

>> empty lun with no partitions is needed.. VMFS partitioned luns cannot be used because VFRC works with VFFS filesystem

2) Can one SSD device be shared by multiple ESXi hosts?

>>   not in vFRC context, normal VMFS datastore on SSD lun can be shared and used for  features like "swap to ssd"

3) Can multiple flash pools be created per ESXi host? If so, what's the maximum number of flash pools can be created per ESXi host?

>>  no, there can be only one pool which will be shared for all VMDK's enabled for using vFRC. as well as swap to SSD if configured.

4) Can a SSD device be used as a local disk?

>> claiming remote as local is possible. but not recommended and performance improvement is not guaranteed in that case with vFRC..

0 Kudos
thuang2
Contributor
Contributor

1a) Can we fake a NFS datastore as a SSD device? 

>>NO

Is there a reason why we cannot fake NFS datastore as a SSD device? Thanks.

0 Kudos
admin
Immortal
Immortal

for using it as cache it needs special filesystem which VMware can control. as NFS filesystem is in NFS server control we can't use it.

As I mentioned earlier we need VFFS filesystem to use a device for vFRC.