Hi Ceez, it's me again...
I hesitated between the 7k1000b (faster arm) and the 7200.12 (more platter throughput), but not the WD for having had dead disks from them (too few to make statistics however).
I bought the 7200.12 but not the 7k1000b so I can't compare experimentally. I chose because I have an Ssd for the OS, so access time was less important for my mechanical drive. If not, I would have kept the
more agile 7k1000.b because my older 7k160 are just better than the others I own or have measured, and are quite silent as well. I own half a dozen of Hitachi and Excelstor equivalent, lost none of them - but a WD yes. And Hitachi is rather known for excellent reliability, though this is linked with model and batch.
The 7200.12 is very silent and I measured
134MB/s platter throughput, the best among 7200rpm disks. Fast capacities are multiples of 250GB here. Random access time, measured over the whole disks, is 1-2ms worse than the good Hitachi (some there are slow as well).
But switch the Aam on at Hitachi, and you get the silence and access time of the 7200.12...
Fast capacities for the 7k1000b are 160GB and multiples of 320GB.
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16MB or 32MB are a
buffer capacity that is never used as a cache and makes no speed difference. Disk manufacturers don't find small Ram chips any more (16MB chips made 128MB modules). Also, customers need something simple to compare.
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I expect Raid-0 to boot slower than a single disk with current 7200rpm technology. Look:
- Windows files may weigh 200kB now (100kB with W95b, 150kB with W2k), so reading at 2*120MB/s takes 833µs fly time instead of 1667µs, gaining 833µs there;
- But rotational latency increases from 1/2 to 2/3 of a turn (7200rpm=120Hz=8,33ms), which loses 1389µs.
- This means that, in a single-queue-depth context, the user would choose a stripe size of 256kB or 512kB nowadays, and typical Windows files would be picked from a single disk.
- But after booting, your uncompressed 15MPixels pictures do load much faster, that's experimentally true.
Already at the 7k80 platter speed (60MB/s, arm as agile as now) I observed it with W2k.
Though, real life is more complicated, especially since Xp and its prefetch, which produces parallel requests to the disks.
As I have
two empty 7200.12 - and the right drivers for W2k and Xp -
I plan to try and observe, so I'll tell you how much slower they are than my X25-E.
This post has been edited by pointertovoid: 09 October 2009 - 06:19 PM