REVENUE Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue
Revenue	$ 85,821	$ 105,789	$ 159,126	$ 211,419
Americas
Disaggregation of Revenue
Revenue	51,718	62,070	92,210	126,022
EMEA
Disaggregation of Revenue
Revenue	24,122	27,935	46,871	54,426
APAC
Disaggregation of Revenue
Revenue	6,504	10,526	13,336	19,259
Primary storage systems
Disaggregation of Revenue
Revenue	20,610	21,299	30,824	35,922
Primary storage systems | Americas
Disaggregation of Revenue
Revenue	16,933	16,352	23,792	25,771
Primary storage systems | EMEA
Disaggregation of Revenue
Revenue	2,798	3,388	5,094	7,226
Primary storage systems | APAC
Disaggregation of Revenue
Revenue	879	1,559	1,938	2,925
Secondary storage systems
Disaggregation of Revenue
Revenue	18,903	28,804	37,395	66,516
Secondary storage systems | Americas
Disaggregation of Revenue
Revenue	9,317	16,004	17,993	40,296
Secondary storage systems | EMEA
Disaggregation of Revenue
Revenue	6,352	8,079	12,968	17,976
Secondary storage systems | APAC
Disaggregation of Revenue
Revenue	3,234	4,721	6,434	8,244
Device and media
Disaggregation of Revenue
Revenue	11,337	18,027	22,318	31,488
Device and media | Americas
Disaggregation of Revenue
Revenue	6,069	9,348	12,431	18,019
Device and media | EMEA
Disaggregation of Revenue
Revenue	4,745	6,640	8,767	10,173
Device and media | APAC
Disaggregation of Revenue
Revenue	523	2,039	1,120	3,296
Service
Disaggregation of Revenue
Revenue	31,494	32,401	61,880	65,781
Service | Americas
Disaggregation of Revenue
Revenue	19,399	20,366	37,994	41,936
Service | EMEA
Disaggregation of Revenue
Revenue	10,227	9,828	20,042	19,051
Service | APAC
Disaggregation of Revenue
Revenue	1,868	2,207	3,844	4,794
Royalty
Disaggregation of Revenue
Revenue	$ 3,477	$ 5,258	$ 6,709	$ 11,712