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#1
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
Hi,
We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? I look forward to your replies. Thanks in advance, Coffeegeek |
#2
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
Previously Coffeegeek wrote:
Hi, We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? I look forward to your replies. Thanks in advance, Coffeegeek The head-parking is not an issue. The drive can secure its hardware on unexpected power loss without problems. What could be an issue is that the OS might not have flushed its data to disk from internal buffers, leaving you with an unusable backup. Typically it works, since, if the system is idle, even non-server OSes like the ones Microsoft makes, flush to disk within seconds. Under load a flush can be delayed up to 5 Minutes (typically) and can then take up to 3 hours for 250GB with the typical USB speed of 25MB/s. So if you remove the disk while it is still being written to or the server is busy with some other disk operations and has not yet written everything to disk, you will get data loss. The only way to be really sure the data is on disk is to use the OSes drive removal function ("remove hardware safely" under Windows, "umount" under practically every Unix) and to wait until it has completed. Arno |
#3
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
"Coffeegeek" wrote in message
ups.com... We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Doesn't matter what order you do this. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? There is no need for this, all drives autopark. You do need to tell the OS you are removing a drive. In Windows, simply use "safely remove drive". This flushes the OS and drive's cache. |
#4
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
"Arno Wagner" wrote in message ... Previously Coffeegeek wrote: Hi, We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? I look forward to your replies. Thanks in advance, Coffeegeek The head-parking is not an issue. The drive can secure its hardware on unexpected power loss without problems. What could be an issue is that the OS might not have flushed its data to disk from internal buffers, leaving you with an unusable backup. Typically it works, since, if the system is idle, even non-server OSes like the ones Microsoft makes, flush to disk within seconds. Under load a flush can be delayed up to 5 Minutes (typically) and can then take up to 3 hours for 250GB with the typical USB speed of 25MB/s. So if you remove the disk while it is still being written to or the server is busy with some other disk operations and has not yet written everything to disk, you will get data loss. By default,Windows XP and Vista disables write caching on any drive it recognises as 'removable' so that should not be an issue. Have a look at the drive properties in device manager and you will see that caching is disabled. -- Kwyj. |
#5
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
Previously Kwyjibo wrote:
"Arno Wagner" wrote in message ... Previously Coffeegeek wrote: Hi, We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? I look forward to your replies. Thanks in advance, Coffeegeek The head-parking is not an issue. The drive can secure its hardware on unexpected power loss without problems. What could be an issue is that the OS might not have flushed its data to disk from internal buffers, leaving you with an unusable backup. Typically it works, since, if the system is idle, even non-server OSes like the ones Microsoft makes, flush to disk within seconds. Under load a flush can be delayed up to 5 Minutes (typically) and can then take up to 3 hours for 250GB with the typical USB speed of 25MB/s. So if you remove the disk while it is still being written to or the server is busy with some other disk operations and has not yet written everything to disk, you will get data loss. By default,Windows XP and Vista disables write caching on any drive it recognises as 'removable' so that should not be an issue. Unless a write is still in progress. This may not even show up as activity on the drive, when the writing programm stops at the moment, e.g. because of waiting for other disk activity. The only way to make sure is to "safely remove". Have a look at the drive properties in device manager and you will see that caching is disabled. It can be activated. So there is an assumption about a non-obvious property to be still in the default setting. Dangerous. In a professional neglient. Arno |
#6
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
Eric Gisin wrote:
"Coffeegeek" wrote in message ups.com... We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Doesn't matter what order you do this. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? There is no need for this, all drives autopark. You do need to tell the OS you are removing a drive. In Windows, simply use "safely remove drive". This flushes the OS and drive's cache. Hello, Eric: Is the "safely remove drive" procedure, an absolute requirement? Since February, I've been solely using the enclosure's power switch, on my SimpleTech "SimpleDrive" (160GB USB external hard disk). Thus far, I haven't noticed any obvious ill effects -- yet, perhaps, there could be more subtle ones? Incidentally, I only employ the SimpleDrive, for daily backup purposes. Thanks, for any advice! Cordially, John Turco |
#7
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
John Turco wrote in
: [snip] Is the "safely remove drive" procedure, an absolute requirement? Yes. Since February, I've been solely using the enclosure's power switch, on my SimpleTech "SimpleDrive" (160GB USB external hard disk). Thus far, I haven't noticed any obvious ill effects -- yet, perhaps, there could be more subtle ones? You'd notice pretty soon - Windows will pop up a message saying a drive was removed improperly and data has been lost. |
#8
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
Previously John Turco wrote:
Eric Gisin wrote: "Coffeegeek" wrote in message ups.com... We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Doesn't matter what order you do this. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? There is no need for this, all drives autopark. You do need to tell the OS you are removing a drive. In Windows, simply use "safely remove drive". This flushes the OS and drive's cache. Hello, Eric: Is the "safely remove drive" procedure, an absolute requirement? Since February, I've been solely using the enclosure's power switch, on my SimpleTech "SimpleDrive" (160GB USB external hard disk). Thus far, I haven't noticed any obvious ill effects -- yet, perhaps, there could be more subtle ones? Incidentally, I only employ the SimpleDrive, for daily backup purposes. Thanks, for any advice! It is the only safe thing to do. True, for many usage patterns, not doing it may work well and only very seldomly lead to data corruption. But it allways can. If you "safely remove", you will not get corruption and you data will be on disk. Arno |
#9
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
"Arno Wagner" wrote in message ... Previously Kwyjibo wrote: "Arno Wagner" wrote in message ... Previously Coffeegeek wrote: Hi, We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? I look forward to your replies. Thanks in advance, Coffeegeek The head-parking is not an issue. The drive can secure its hardware on unexpected power loss without problems. What could be an issue is that the OS might not have flushed its data to disk from internal buffers, leaving you with an unusable backup. Typically it works, since, if the system is idle, even non-server OSes like the ones Microsoft makes, flush to disk within seconds. Under load a flush can be delayed up to 5 Minutes (typically) and can then take up to 3 hours for 250GB with the typical USB speed of 25MB/s. So if you remove the disk while it is still being written to or the server is busy with some other disk operations and has not yet written everything to disk, you will get data loss. By default,Windows XP and Vista disables write caching on any drive it recognises as 'removable' so that should not be an issue. Unless a write is still in progress. Read it again. I said 'write caching' should not be an issue as it is disabled. If a write is in progess but caching is disabled I agree that it could cause problems, but those problems have absolutely nothing to do with write caching. If you are going to bother replying, please try to ensure that your post is factually accurate. -- Kwyj. |
#10
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Do you need to 'eject' USB HDD? Do they auto park at power-off?
Previously Kwyjibo wrote:
"Arno Wagner" wrote in message ... Previously Kwyjibo wrote: "Arno Wagner" wrote in message ... Previously Coffeegeek wrote: Hi, We are using two USB hard drives (250gb) as backup for our companies system. Each is used to contain a complete image of the entire server, and is swapped over every night with the other. There is a power switch on the housing, which we have been turning off, then disconnecting the drive, connect the new one, then turn it's switch on. Does anyone know if turning off with this switch will let the drive park it's heads, or should we still go through the full 'eject' hardware (soft switch) route? I look forward to your replies. Thanks in advance, Coffeegeek The head-parking is not an issue. The drive can secure its hardware on unexpected power loss without problems. What could be an issue is that the OS might not have flushed its data to disk from internal buffers, leaving you with an unusable backup. Typically it works, since, if the system is idle, even non-server OSes like the ones Microsoft makes, flush to disk within seconds. Under load a flush can be delayed up to 5 Minutes (typically) and can then take up to 3 hours for 250GB with the typical USB speed of 25MB/s. So if you remove the disk while it is still being written to or the server is busy with some other disk operations and has not yet written everything to disk, you will get data loss. By default,Windows XP and Vista disables write caching on any drive it recognises as 'removable' so that should not be an issue. Unless a write is still in progress. Read it again. I said 'write caching' should not be an issue as it is disabled. If a write is in progess but caching is disabled I agree that it could cause problems, but those problems have absolutely nothing to do with write caching. And neither did I claim it does. There are two problems here. Open files by an application and write-caching by the OS. To nit-pick, the application itself could also do some form of write-caching, although that is rather rare. If you are going to bother replying, please try to ensure that your post is factually accurate. I did. Maybe you should read my posting again? Arno |
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