RAID Performance Calculators
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Then the question becomes, is it worth the expense of going to SSD?
Even buying consumer drives (say 480GB drive for $150 yesterday), maxing that out at 8 drives in RAID 5 gives me 3.3 TB and insane IOPs. More than my controller can handle.
But is that the smart spend? In my case probably not. I can get 2 TB NL SAS drives for $80. Put them in a RAID 6, giving me 12 TB usable and roughly (8 * 70 IOPs) 540 IOPs (something less due to RAID 6). In my case, backup storage, this is probably enough IOPs, and I'd be at 4 times the storage and 1/2 the cost.
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@Dashrender said:
Then the question becomes, is it worth the expense of going to SSD?
But don't forget that SSDs have the power saving advantage to offset their cost too. Even at only $50 a drive, that can be a big percentage of the different in per drive costs.
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@Dashrender said:
But is that the smart spend? In my case probably not. I can get 2 TB NL SAS drives for $80. Put them in a RAID 6, giving me 12 TB usable and roughly (8 * 70 IOPs) 540 IOPs (something less due to RAID 6). In my case, backup storage, this is probably enough IOPs, and I'd be at 4 times the storage and 1/2 the cost.
R6 has a 6x write hit. But NL-SAS drives should deliver a lot more than 70 IOPS. More like 140 IOPS. NL-SAS is faster than 7200 RPM SATA which is 50% faster than 5400 RPM SATA.
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With good queue depth you can get well over 100 IOPS from a WD Red or WD Green which are 5400 RPM SATA drives.
So if 5400 RPM SATA can push 120 IOPS, 7200 RPM SATA should close in on 170 IOPS. The same spindle on SAS generally gets 5% - 20% improvement over that. So reasonable to see 200 IOPS from NL-SAS.
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So 8 * 150, as a more reasonable starting point, is 1,200 RIOPS from an OBR6 array. But only 200 WIOPS. So your blend is important.
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And, of course, this is from the array itself. The RAID controller should have a RAM cache. That can, depending on the workload, make a truly massive difference especially if you have 1GB or more.
