Xtremcache

Hi,

It depends on what do you understand by "write cache".

The way XtremSW works is that every time you write something to the accelerated LUN, the same data will be asynchronously written to the cache, so in case the application needs to read it, it will read it from the cache, not the backend device.

XtremSW driver will not acknowledge the write until it's completed by the array though, so it doesn't behave like a write cache on, say, VMAX where the write is acknowledged once it hits the cache memory, not backend disks - so if that's something you are looking for, it cannot be done with XtremSW.

You can achieve write buffering if you use RAID controllers for the ScaleIO disks - they usually have some write caches enabled.

P.

Is there any difference between Xtremcache and scaleIO RAM read cache?

Thanks.

ScaleIO RAM cache utilizes RAM on the SDS and doesn't require any other equipment, while XtremSW requires a special card as well as the software.

If there are very large available RAM memory (which could be used as RAM cache)on SDS,is it needed to configure XtremSW  cache?

Nope. ScaleIO has a built in function of READ RAM CACHE that can be invoked.

Please refer to the Managing RAM read cache section in the User Guide for further info.