I keep a spreadsheet handy just for quick reference with the amount of IOPS a raid group can handle given the write profile, raid type, and # of disks.  I've included that.  I find it easier than doing the math every time.

  I'd look at analyzer (LUN Level) and see what your read/write ratio is on average.  I'd also probably look the LUN to see the throughput (IOPS) of the LUN.  I'd also check response time of the LUN and make sure it's an acceptable response time.  If not, more spindles might be needed.

The formula I use to calculate IOPS for a given # of disks is.

IOPS = SingleDiskIOPS * #OfDisks / (ReadRatio + (WritePenalty * WriteRatio)

RAID 5 = 4 write penalty

RAID 10 = 2 write penalty

I use 180 IOPS for 15k rpm and 130 for 10k RPM drives.

i.e Raid5 with 5 disks 20% write 15k rpm drives

(180 * 5) / (.8 + (.2 *4)) = 562.5 IOPS

If you're doing MetaLUNs, calculate the IOPS for 1 RAID group, then just multiply that by the # of RAID groups the MetaLUN spans.

	Fibre Channel 15k								Fibre Channel 10k
Disk Count	R5 100% Write Available IOPS	R5 100% Read Available IOPS	R5 20% Write 80% Read Available IOPS	R5 33% Write 67% Read Available IOPS	R1+0 100% Write Available IOPS	R1+0 100% Read Available IOPS	R1+0 20% Write 80% Read Available IOPS	R1+0 33% Write 67% Read Available IOPS	R5 100% Write Available IOPS	R5 100% Read Available IOPS	R5 20% Write 80% Read Available IOPS	R5 33% Write 67% Read Available IOPS	R1+0 100% Write Available IOPS	R1+0 100% Read Available IOPS	R1+0 20% Write 80% Read Available IOPS	R1+0 33% Write 67% Read Available IOPS
2					180	360	300.00	270.68					130	260	216.67	195.49
3	135	540	337.50	271.36					97.5	390	243.75	195.98
4	180	720	450.00	361.81	360	720	600.00	541.35	130	520	325.00	261.31	260	520	433.33	390.98
5	225	900	562.50	452.26					162.5	650	406.25	326.63
6	270	1080	675.00	542.71	540	1080	900.00	812.03	195	780	487.50	391.96	390	780	650.00	586.47
7	315	1260	787.50	633.17					227.5	910	568.75	457.29
8	360	1440	900.00	723.62	720	1440	1200.00	1082.71	260	1040	650.00	522.61	520	1040	866.67	781.95
9	405	1620	1012.50	814.07					292.5	1170	731.25	587.94
10	450	1800	1125.00	904.52	900	1800	1500.00	1353.38	325	1300	812.50	653.27	650	1300	1083.33	977.44
11	495	1980	1237.50	994.97					357.5	1430	893.75	718.59
12	540	2160	1350.00	1085.43	1080	2160	1800.00	1624.06	390	1560	975.00	783.92	780	1560	1300.00	1172.93
13	585	2340	1462.50	1175.88					422.5	1690	1056.25	849.25
14	630	2520	1575.00	1266.33	1260	2520	2100.00	1894.74	455	1820	1137.50	914.57	910	1820	1516.67	1368.42

Be careful about metaLUN performance - it's more complicated than just taking the number of components - you have to consider raid type, number of disks in the underlying raid groups, whether or not you're reusing the same raid group (not generally a good idea), etc.

glen

great info!

Does anyone have any details on the VNX performance pleaseeeeee

telling people its 3 times faster than the clariion with ouit some detail is not working with customers :-)