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#1
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which RAID level for write only?
I would like to know which raid level is the best for Write operation.
I am considering Raid 0, Raid 1 , Raid 0+1, Raid 10, Raid 3, and Raid 5. Also, are there any Raid Storage support Raid4, except NetApp? TIA |
#2
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It depends on if you actually want the Redundancy part of RAID, if you want
speed do RAID 0 (Stripe), if there is lots of sequential stuff then RAID 3 would be a safe bet. Regards Mark "Tester A." wrote in message ... I would like to know which raid level is the best for Write operation. I am considering Raid 0, Raid 1 , Raid 0+1, Raid 10, Raid 3, and Raid 5. Also, are there any Raid Storage support Raid4, except NetApp? TIA |
#3
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Yes, I need redundacy, so RAID 0 is not the option for me.
Also, the files that are written is email messages backup, which is very small. This is the backup server, so not much read access is there, unless the main server is broken. Raid 3 is better than other levels for write operation? "Mark" wrote in message ... It depends on if you actually want the Redundancy part of RAID, if you want speed do RAID 0 (Stripe), if there is lots of sequential stuff then RAID 3 would be a safe bet. Regards Mark "Tester A." wrote in message ... I would like to know which raid level is the best for Write operation. I am considering Raid 0, Raid 1 , Raid 0+1, Raid 10, Raid 3, and Raid 5. Also, are there any Raid Storage support Raid4, except NetApp? TIA |
#4
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On Mon, 15 Sep 2003 02:21:53 GMT, "Tester A."
wrote: I would like to know which raid level is the best for Write operation. I am considering Raid 0, Raid 1 , Raid 0+1, Raid 10, Raid 3, and Raid 5. Also, are there any Raid Storage support Raid4, except NetApp? RAID-4 buys you (as a consumer) nothing, and its presence in NetApp products is an artifact of their development priorities/processes. If your I/O operations are many and small, then either RAID-5 or a stripe of RAID-1 (sometimes called RAID-10 by the marketroids) is what you want. If they are few and large, you want (true) RAID-3. If your performance following a drive failure is critical, RAID-3. Simple math: With N disks, the maximum number of simultaneous write ops is: RAID-1: (N/2) RAID-3: 1 RAID-4: 1 RAID-5: (N-1)/2 [ Obviously, in the case of RAID-3, the time taken for the write is dramatically improved over the time taken by a single disk. In the other cases, the write time is (very roughly) somewhere between one and two times that of a single disk. ] Malc. |
#5
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In article ,
Malcolm Weir wrote: RAID-4 buys you (as a consumer) nothing, and its presence in NetApp products is an artifact of their development priorities/processes. NetApp isn't really RAID-4 in the normal sense, is it? I was under the impression that it was actually handled at the file system level. -- I've seen things you people can't imagine. Chimneysweeps on fire over the roofs of London. I've watched kite-strings glitter in the sun at Hyde Park Gate. All these things will be lost in time, like chalk-paintings in the rain. `-_-' Time for your nap. | Peter da Silva | Har du kramat din varg, idag? 'U` |
#6
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On Mon, 15 Sep 2003 18:19:47 +1200, "Mark" wrote:
It depends on if you actually want the Redundancy part of RAID, if you want speed do RAID 0 (Stripe), if there is lots of sequential stuff then RAID 3 would be a safe bet. Regards Mark When should one choose RAID 3 over RAID 10? Both perform well. |
#7
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"idunno" wrote in message ... On Mon, 15 Sep 2003 18:19:47 +1200, "Mark" wrote: It depends on if you actually want the Redundancy part of RAID, if you want speed do RAID 0 (Stripe), if there is lots of sequential stuff then RAID 3 would be a safe bet. Regards Mark When should one choose RAID 3 over RAID 10? Both perform well. Cost would be a factor with RAID 10 you need more physical drives than you would with a RAID 3 or 5 setup. Mark |
#8
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"Mark" wrote in message ...
"idunno" wrote in message ... On Mon, 15 Sep 2003 18:19:47 +1200, "Mark" wrote: It depends on if you actually want the Redundancy part of RAID, if you want speed do RAID 0 (Stripe), if there is lots of sequential stuff then RAID 3 would be a safe bet. Regards Mark When should one choose RAID 3 over RAID 10? Both perform well. Cost would be a factor with RAID 10 you need more physical drives than you would with a RAID 3 or 5 setup. Mark RAID 5 is versatile all-around good performer (on good cards only I might add) but is not the highest performer when it comes to writes. RAID 3 and 10 are both intended for high throughput applications that require fault-tolerance. Yes RAID 3 and 5 have a better ratio of ECC disk space to data disk space, but I was wondering if there is also a significant performance difference in disk writes or whether certain environments prefer RAID 3 or 10 on a _strictly_ performance basis. |
#9
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"idunno" wrote in message om... .... RAID 5 is versatile all-around good performer (on good cards only I might add) but is not the highest performer when it comes to writes. RAID 3 and 10 are both intended for high throughput applications that require fault-tolerance. Yes RAID 3 and 5 have a better ratio of ECC disk space to data disk space, but I was wondering if there is also a significant performance difference in disk writes or whether certain environments prefer RAID 3 or 10 on a _strictly_ performance basis. For small writes, a classic RAID-3 implementation may be slightly faster because its spindles are synchronized (and the mirrored spindles in RAID-10 typically aren't, so the write there will take take the longer of the two disk access times). But if the RAID-10 controller has stable write-back cache such that it can queue up write requests and execute them in optimal order, any such advantage may be reduced or eliminated (as it will be for large writes in any event, where the access times become a smaller percentage of the overall overhead). But that's for purely serial small writes. For multiple small writes requested in parallel, RAID-10 may well be able to process at least some of them in parallel, whereas RAID-3 will serialize them at the parity disk (though should at least be able to queue-optimize their execution). RAID-10, of course, provides potentially significantly better *read* performance for a given usable capacity. It also provides somewhat better availability, since with RAID-3 (or -5) the loss of any two disks results in data loss whereas with RAID-10 data is lost only if the two disks happen to be partners. - bill |
#10
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"Bill Todd" wrote in message ...
For small writes, a classic RAID-3 implementation may be slightly faster because its spindles are synchronized (and the mirrored spindles in RAID-10 typically aren't, so the write there will take take the longer of the two disk access times). But if the RAID-10 controller has stable write-back cache such that it can queue up write requests and execute them in optimal order, any such advantage may be reduced or eliminated (as it will be for large writes in any event, where the access times become a smaller percentage of the overall overhead). But that's for purely serial small writes. For multiple small writes requested in parallel, RAID-10 may well be able to process at least some of them in parallel, whereas RAID-3 will serialize them at the parity disk (though should at least be able to queue-optimize their execution). RAID-10, of course, provides potentially significantly better *read* performance for a given usable capacity. It also provides somewhat better availability, since with RAID-3 (or -5) the loss of any two disks results in data loss whereas with RAID-10 data is lost only if the two disks happen to be partners. - bill Thank you. That helps. Are these performance differences maintained when you enable spindle sync on a RAID 10 array with a large write-back cache? |
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