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A question on write caching
I'm planning to add a new 120gb drive to my system, but I'm not sure
if I should take a 2Mb or 8Mb cache version. What bothers me is the following thought: If current hard drives cache writing operations, isn't the risk of data loss (by power failure etc.) higher with 8mb of cache? I'm thinking along the lines that if more data is cached, more time is needed to write it away, so the "window of opportunity" for data loss is longer. I also seem to remember a windows bug where an ATX system would power down too fast for disk writes to complete. So my questions a - Is the risk of data loss really higher with a larger cache? - Is write caching enabled by default on today's drives? (I'm planning to get either a WD1200BB (2mb) or WD1200JB (8mb).) - If there's write caching, is it set to write-through or write-back by default? Thanks, Robert |
#2
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"Robert Mischke" wrote in message ... I'm planning to add a new 120gb drive to my system, but I'm not sure if I should take a 2Mb or 8Mb cache version. What bothers me is the following thought: If current hard drives cache writing operations, isn't the risk of data loss (by power failure etc.) higher with 8mb of cache? The data doesn't stay in the cache for long. Anyway why worry about 2 vs 8 MByte when you have 512 MByte of main memory? Perhaps you should take some of that out and send it to me :-) |
#3
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"Robert Mischke" wrote in message ... I'm planning to add a new 120gb drive to my system, but I'm not sure if I should take a 2Mb or 8Mb cache version. What bothers me is the following thought: If current hard drives cache writing operations, isn't the risk of data loss (by power failure etc.) higher with 8mb of cache? Yes. I'm thinking along the lines that if more data is cached, more time is needed to write it away, so the "window of opportunity" for data loss is longer. I also seem to remember a windows bug where an ATX system would power down too fast for disk writes to complete. Fixed. So my questions a - Is the risk of data loss really higher with a larger cache? Probably but that doesn't specify the absolute value of the overall risk which is generally low in many average situations. - Is write caching enabled by default on today's drives? Yes. (I'm planning to get either a WD1200BB (2mb) or WD1200JB (8mb).) - If there's write caching, is it set to write-through or write-back by default? Write back. On board writethrough is what happens when onboard caching is off. |
#4
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"Ron Reaugh" wrote in message ... If current hard drives cache writing operations, isn't the risk of data loss (by power failure etc.) higher with 8mb of cache? Yes. No. I don't believe it makes any difference. The only "safe" place for data is on the drive platter itself and a larger cache DOES NOT slow down the overall process of writing data to the platter - that's fixed by the bit rate/rpm etc. |
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#6
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CWatters wrote:
"Robert Mischke" wrote in message ... I'm planning to add a new 120gb drive to my system, but I'm not sure if I should take a 2Mb or 8Mb cache version. What bothers me is the following thought: If current hard drives cache writing operations, isn't the risk of data loss (by power failure etc.) higher with 8mb of cache? The data doesn't stay in the cache for long. Anyway why worry about 2 vs 8 MByte when you have 512 MByte of main memory? Perhaps you should take some of that out and send it to me :-) I think that misses the point. Losing data in the drive cache can leave the drive in an inconsistent state. Losing data in the main memory, even if it's cached disk writes, won't result in an inconsistent state if you use a logging file system. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#7
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Robert Mischke wrote:
I'm planning to add a new 120gb drive to my system, but I'm not sure if I should take a 2Mb or 8Mb cache version. What bothers me is the following thought: If current hard drives cache writing operations, isn't the risk of data loss (by power failure etc.) higher with 8mb of cache? I'm thinking along the lines that if more data is cached, more time is needed to write it away, so the "window of opportunity" for data loss is longer. I also seem to remember a windows bug where an ATX system would power down too fast for disk writes to complete. So my questions a - Is the risk of data loss really higher with a larger cache? - Is write caching enabled by default on today's drives? (I'm planning to get either a WD1200BB (2mb) or WD1200JB (8mb).) - If there's write caching, is it set to write-through or write-back by default? Thanks, Robert The real problem with some IDE drives is you can't turn the write cache off (at least I've seen drives where I couldn't -- the software would say it had done so, but when I checked afterwards the cache was still on). -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#8
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Thanks for all the answers!
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