Degraded E-Series read latency on flash read cache enabled volume
Applies to
- NetApp E-Series
- NetApp StorageGRID Appliance (SG6060)
- Single and Dual controller storage array systems using flash read cache (FRC)
- SANtricity OS 11.70.4+
Issue
- Higher read latency was noticed on flash read cache (FRC) enabled volumes after upgrade to SANtricity OS 11.70.4 or later release.
- In E-Series support data or controller shell, this command
tditlnall 3shows the volume (LUN ID) read and write I/O latency. Comparing the latency against pre-11.70.4, the average latency increased from sub-millisecond to multiple milliseconds.
Pre-11.70.4 SANtricity OS
-> tditlnall 3
Read/Write Completions
.........TDITLN.........:Initiator.:.................R E A D S................:...............W R I T E S................:
tditn LUN LU(SSID) Ch : Location : #Success ByteXfered ART(uSec) MRT(uSec) : #Success ByteXfered ART(uSec) MRT(uSec) :#Errs
------- --- -------- -- :--------- :---------- ---------- --------- --------- :---------- ---------- --------- --------- :-----
4 253 00000004 2 :0x1000001 : 17247959 477464117248 235 664446 : 933375 48351206400 1735 1128777 : 0
6 253 00000004 3 :0x1000001 : 17224923 476861496320 236 647369 : 924492 48300143104 1780 1226118 : 0
11.70.4+ SANtricity OS
-> tditlnall 3
Read/Write Completions
.........TDITLN.........:Initiator.:.................R E A D S................:...............W R I T E S................:
tditn LUN LU(SSID) Ch : Location : #Success ByteXfered ART(uSec) MRT(uSec) : #Success ByteXfered ART(uSec) MRT(uSec) :#Errs
------- --- -------- -- :--------- :---------- ---------- --------- --------- :---------- ---------- --------- --------- :-----
4 253 00000004 4 :0x1000001 : 17167803 463487405056 9150 2510841 : 1038936 58143469568 845 1078669 : 0
6 253 00000004 5 :0x1000001 : 17149289 462841043456 9172 2553690 : 1026237 58029947392 886 1166025 : 0