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I am new to the whole SSD thing, but I don't understand how the following works?

I need to be very specific for this question to make sense.

1 x LSI MegaRAID SAS 9361-8i 570$
8 x Ultrastar SSD800MH MLC 200GB 8x1450 = 11.600$
Total cost: 12.170$

Expected performance in RAID 0:
read: 140x8 = 1.120.000 IOPS
write: 100x8 = 800.000 IOPS
space: 200x8 = 1.6TB

On the other hand we have:

ioDrive2 Duo 1.2TB SLC Total cost: 28.500$

Expected performance:
read: 580.000 IOPS
write: 535.000 IOPS
space: 1.2TB

One will say: RAID 0 will fail. But the truth is ioDrive2 Duo can also fail, so you have to buy 2 and RAID 1 them.

I understand the different between SLC and MLC (performance and durability), but the Ultrastar drives seems really solid and unless you torment them, they won't die.

All in all, what is wrong with my calculations? Why people buy those PCIe cards and they don't build arrays of drives? It's more simple to manage, but it costs more than double?

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  • Just a reminder: RAID is not backup. Mar 7 '14 at 11:03
  • Is it a good idea to just use one PCIe SSD? I mean, if it fails, is there any way to get the data?
    – Luka
    Mar 7 '14 at 11:22
  • No, but if one of your eight SSDs in RAID-0 fails, which is far more likely, there's no way to get your data either. Mar 7 '14 at 11:26
  • Then you have to buy 16 SSDs and 2 RAID controllers = 23.200$ vs 2 ioDrive2 Duo = 57.000$
    – Luka
    Mar 7 '14 at 12:03
  • possible duplicate of Do I need to RAID Fusion-io cards?
    – ewwhite
    Mar 7 '14 at 12:41
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We use both FusionIO kit and lots of top-end SSDs, and we have seen failures in both but with the FusionIO we've not had anything that caused data loss, RAID 0 will kill your data one day, it's not an 'if', it's a 'when'.

Now onto your calculations, the FusionIO stats are about what we see too but are you sure that LSI card can actually deliver 1.1m IOPS? I'm guessing you'd have to split the disks across all channels to get close to that?

We buy the PCIe cards because they're really consistent, there's less 'parts' and complexity involved, they're not pretending to be a spinny-disk so the latency is lower. Yes they can be more expensive (we perhaps get better pricing on those to be honest) but for what we use them for they're better overall value - that said we use SSDs in R10, I'd never consider a R0 setup.

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