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Maximum Speeds for SATA Drives
When a SATA drive employs more than one cylinder, are they striping data
across the cylinders transparently, or are they just laying out data contiguously on any given track / cylinder? I have someone telling me that they have been measuring 150 MB / second throughputs on individual SATA drives, which is way beyond what a 7200 rpm rotation speed on an individual track should be able to give you. I think they are probably measuring a transfer speed out of a cache and don't realize it. I've seen various consumer SATA RAID arrays record write throughputs around 30 to 60 MB/second, which implies that the individual drives rarely deliver more than 15 MB / second, and that would be for contiguous data. What kinds of performance numbers have others seen for individual SATA drives where the data is fragmented? Any insights on performance of individual SATA drives is appreciated. -- Will |
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Maximum Speeds for SATA Drives
In article ,
Will wrote: I've seen various consumer SATA RAID arrays record write throughputs around 30 to 60 MB/second, which implies that the individual drives rarely deliver more than 15 MB / second, and that would be for contiguous data. I suppose if you're uninterested in the facts it implies that. A trivial test will determine that for contiguous data even the cheapest modern SATA drives write at about three to four times the rate you quote. Look elsewhere for the explanation for poor long write performance with SATA RAID arrays. It's not the write rate of the underlying drives that's the problem. -- Thor Lancelot Simon "The inconsistency is startling, though admittedly, if consistency is to be abandoned or transcended, there is no problem." - Noam Chomsky |
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Maximum Speeds for SATA Drives
"Thor Lancelot Simon" wrote in message
... In article , Will wrote: I've seen various consumer SATA RAID arrays record write throughputs around 30 to 60 MB/second, which implies that the individual drives rarely deliver more than 15 MB / second, and that would be for contiguous data. I suppose if you're uninterested in the facts it implies that. A trivial test will determine that for contiguous data even the cheapest modern SATA drives write at about three to four times the rate you quote. How are they doing this? They are striping data across four or more platters? -- Will |
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Maximum Speeds for SATA Drives
I've seen various consumer SATA RAID arrays record write throughputs around
30 to 60 MB/second, which implies that the individual drives rarely deliver more than 15 MB / second, and that would be for contiguous data. 70MB/s is OK for more-or-less modern SATA drive. The run seems to be long enough to not be influenced by the cache. -- Maxim Shatskih, Windows DDK MVP StorageCraft Corporation http://www.storagecraft.com |
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Maximum Speeds for SATA Drives
"Will" writes:
SATA drives write at about [50-60 MB/sec] How are they doing this? They are striping data across four or more platters? No. They are using higher densities than you seem to be assuming. |
#6
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Maximum Speeds for SATA Drives
"Maxim S. Shatskih" wrote in message
... I've seen various consumer SATA RAID arrays record write throughputs around 30 to 60 MB/second, which implies that the individual drives rarely deliver more than 15 MB / second, and that would be for contiguous data. 70MB/s is OK for more-or-less modern SATA drive. The run seems to be long enough to not be influenced by the cache. Wow, amazing. What is the easiest way to setup a test to show that performance level on a single drive? -- Will |
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Maximum Speeds for SATA Drives
"Will" wrote in message
... 70MB/s is OK for more-or-less modern SATA drive. The run seems to be long enough to not be influenced by the cache. Wow, amazing. What is the easiest way to setup a test to show that performance level on a single drive? -- Will Boot a stand-alone Linux CD that supports your SATA adapter and then run a large 'dd' directly from the raw drive device. Something like: # time `dd if=/dev/hda of=/dev/null bs=32k count=1000000` Rob |
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Maximum Speeds for SATA Drives
Boot a stand-alone Linux CD that supports your SATA adapter and then run a
large 'dd' directly from the raw drive device. Something like: # time `dd if=/dev/hda of=/dev/null bs=32k count=1000000` Playing with "bs" is also a good idea. (S)ATA protocol has a natural block size of 64K. -- Maxim Shatskih, Windows DDK MVP StorageCraft Corporation http://www.storagecraft.com |
#9
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Maximum Speeds for SATA Drives
"Maxim S. Shatskih" wrote in message
... Boot a stand-alone Linux CD that supports your SATA adapter and then run a large 'dd' directly from the raw drive device. Something like: # time `dd if=/dev/hda of=/dev/null bs=32k count=1000000` Playing with "bs" is also a good idea. (S)ATA protocol has a natural block size of 64K. So if you were going to be copying large files to a single SATA device, would using a Windows "Allocation Unit" of 64K when formatting the drive make any sense? On SATA drives I've generally seen the throughput maximize when I make Windows allocation units 8K, and performance degrades a bit at 16K and 32K. I haven't tried 64K. -- Will |
#10
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Maximum Speeds for SATA Drives
Will wrote:
"Maxim S. Shatskih" wrote in message ... Boot a stand-alone Linux CD that supports your SATA adapter and then run a large 'dd' directly from the raw drive device. Something like: # time `dd if=/dev/hda of=/dev/null bs=32k count=1000000` Playing with "bs" is also a good idea. (S)ATA protocol has a natural block size of 64K. So if you were going to be copying large files to a single SATA device, would using a Windows "Allocation Unit" of 64K when formatting the drive make any sense? On SATA drives I've generally seen the throughput maximize when I make Windows allocation units 8K, and performance degrades a bit at 16K and 32K. I haven't tried 64K. Any reasonably-competent Copy function will preallocate the entire output file prior to initiating the data copying, so the allocation unit size should be irrelevant (unless the free space on the disk is severely fragmented). - bill |
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