Which chipsets support hot-UNplugging of HDDs under Win XP?

Skazka · Post by **Skazka** » Mon Jul 30, 2007 11:44 am

Hi,

I am from Moscow, Russia. I would like to ask a couple of questions, if I may, since Iâ€™m desperately trying to get the answers to my questions at Russian forums.

It is known that hot-plugging for SATA II hard drives has been realized in south bridges ICH7 and ICH9 (with the indexes R, DH, DO). With the AHCI driver installed for Windows XP hot-plugging is stabile and as it should be.
In Intel documentation for the chipsets, for motherboards and for the company utility Matrix Storage there is no word about hot-unplugging.
I am interested in the answers to my following questions:
1. Has hot unplugging of hard drives been realized in ICH7 and 9 controllers under Windows XP control and how secure is the hot-unplugging? Could be the hard drive turned safely off by clicking the icon of HDD in the System Tray?
2. Does the operation of AHCI as a whole and hot-unplugging particularly differ in ICH9 and ICH7?
3. Would it be possible to stop and then to start spindle of a hard drive under Windows XP control with standard means of the controller and BIOS?

My questions are caused by the following thoughts. If several hard drives are used in a personal computer and some of them are used exceptionally for the information storage, to lower the risks of loss of their content and decrease the hard drive noise it would be not a bad solution to organize secure hot plugging/unplugging of these hard drives. By that to insure maximum reliability it would be useful to stop the disc spindle after hot unplugging and start it before the hot plugging.
Of course, external UBS hard drives could be used to realize hot plugging and Mobile racks for the disc power shut down and Windows Device Manager for hard drives logical disable/enable as well. However, I want to solve the problem with the hot-unplugging function. And here is why.
External USB discs are no good since it is quite expensive, you need some space for several discs storage, new wires appear, and the most important is the lower speed compared with SATA II. The problem could be partially solved with the use of internal USB discs, but as I know they are not produced. As far as the Mobile racks use they do not insure discs safe hot unplugging (at least mass models) since they could be used for my purposes only as a button for power turn off of the hard disc. If the complete power shut down is not required and only the disc spindle needs to be stopped you could manage it with hdparm program with the -s key (or with the standard means of the controller, if they are available). Especially I am planning to assemble a quiet computer and place all discs in boxes of Scythe Quiet Drive type, whereas Mobile racks does not substantially decrease the noise of the hard drives.
Windows Device Manager does not allow to securely turn off the disc. If you turn off the hard disc and at this moment the operational system all over sudden addresses to the disc then the computer may hang or partial loss of the information on the hard drive may occur.
So the only possibility for me is to insure the hot-unplugging of several internal SATA II discs in my computer.
New Intel motherboards oriented on mass market appeared now where a set of x35 chipset and Southbridge ICH9 (R, DH, DO) are used. For example DP35DP motherboard. Such motherboards are relatively inexpensive and at the same time they are quite reliable. On the other hand the price for old motherboards on the basis of i975 chipset with Southbridge ICH7 (R, DH, DO) is still quite expensive. For example the D975XBX2 and S975XBX2 motherboard.
Couldnâ€™t be such price difference explained by the fact that the old controller ICH7 (R, DH, DO) ensured higher reliability in operation of AHCI, easier AHCI driver installation for Windows XP or broader hard discs controlling functions?
At this point in time I decided to stop my selection on Intel motherboard and I want to assemble a reliable PC (of course I will not overclock my PC). Thatâ€™s why I select between D975XBX2 and DP35DP since I need Intel motherboard with ATX form-factor which has COM-port and which doesnâ€™t have incorporated graphics. I cannot come to a solution which of the motherboards between the two to pick up. I have doubts particularly on hot-unplugging (if such function is possible at all) of these motherboards and functional features of AHCL operation.

I would appreciate any of your replies.

tibetan mod king · Post by **tibetan mod king** » Mon Jul 30, 2007 12:27 pm

It is not safe to "hot unplug" drives. You can reduce the risk by turning off the write cache at the drive, controller, driver, and OS levels. However, you take a massive performance hit when you disable all the write caches. Maybe for read only content, there is some sense in "hot unplug". But this is tricky in the Windows environment (to say the least).

What I do is use a 3ware controller. Through the 3ware controller web interface, I can add/remove a drive (logically). After telling the controller a particular drive has been removed, I then use a KEYED mechanism to cut power to the drive. I then let it spin down for 30++ seconds. It is only then that I remove the drive. This is all for a "hot swap" drive, in a "hot swap" drive bay, using a "hot swap" controller.

Another idea I have considered is using a web-controlled power distribution system and a large number of external drives (say using Antec MX-1 enclosures -- see the review on this site). This gives you web access to turn on/off any particular set of drives. Take a bit of space, but gives you very fine grain control over how many drives are powered up at any given time. I would hook these drives up using eSATA, not USB2.

The bolder statement is to simply put your mass storage in a place where noise does not matter and then use iSCSI to access it all. iSCSI is quite fast for most purposes and gives you amazing flexibility on where drives can be located.

Let me know what you think of these possibilities.

alglove · Post by **alglove** » Mon Jul 30, 2007 3:04 pm

Hmmm, as I understand it, Skazka is talking about hot-unplugging the drives by going to the Windows system tray (down by the clock) and using the "Safely Stop/Remove a Device" icon. As I understand it, this makes going into the Device Manager and disabling all the write caching options unnecessary. That is the whole purpose of this icon.

I do not believe that Skazka literally meant "hot-unplugging", as in, "disconnecting the power from the drive without any warning". Of course, the SATA power plug is meant to support this safely, but on a data level, it is not safe, for all the reasons Tibetan mentioned.

Unfortunately, I do not have in particular insight into the Intel ICH7/ICH9 issue. The only chipsets I have used with SATA drives are the VIA KT880 (8327R southbridge, supports only "SATA-I") and the NVIDIA nForce Professional 3400. From my limited experience, "Safely Removing" the SATA drive seems to work fine with the VIA chipset (WinXP), but the NVIDIA chipset (Win2k3 server) does not seem to support it at all.

Bear in mind that I do not actually own an SATA drive at the moment, so my personal experience with both configurations is rather limited. Anybody with other experiences should surely feel free to add comments.

I wonder if there is some sort of way through the Windows power management to put the hard drive to "sleep" before "safely removing" it. I would think that it should be possible, at least in theory. I would guess that it may be easier in Vista, which has much more detailed control over the computer's power management.

frank2003 · Post by **frank2003** » Mon Jul 30, 2007 3:52 pm

alglove wrote: I wonder if there is some sort of way through the Windows power management to put the hard drive to "sleep" before "safely removing" it.

I have not tried this, but the following may cause Windows to "flush" the disk write buffers:

1 - In Device Manager, disable the disk, or
2 - In Disk Management>Change Drive Letter and Paths, remove the drive letter.

Max Slowik · Post by **Max Slowik** » Mon Jul 30, 2007 4:02 pm

I wonder if there is some sort of way through the Windows power management to put the hard drive to "sleep" before "safely removing" it.

Yeah, there is, with SATA drives ONLY. Click on the removable devices icon in the system tray, select the hard drive you want to disconnect, and stop it. Then you can unplug it. You don't have to do anything special to plug in a drive. This also stops the caching so you don't have to worry about data loss.

This way is safe and supported by Microsoft, and I use it all the time with open test benches, since I don't have a personal file server set up yet, but I do have a big ol' stack of hard drives.

Max Slowik · Post by **Max Slowik** » Mon Jul 30, 2007 4:03 pm

Oh, and another thing: you can't disconnect an OS partition this way, even if it shows up in the removable devices manager; MS is smart and dumb like that. You can't remove any drive in use, actually.

tibetan mod king · Post by **tibetan mod king** » Mon Jul 30, 2007 5:51 pm

I think much depends on the specifics of your disk driver and/or disk controller.

For example, in the 3ware world (I know, not the world of the OP, but I am using it as an example):

FUA (Force Unit Access). FUA commands are a way that the RAID controller or a program (such as a database program) can ensure that data is actually written to the disk drive media, and is not stored in cache. When a write command is followed with a FUA command, then the disk drive will only issue "command complete" to the controller once the data is written to media. When performance is considered more important than protection, it may be desirable to ignore FUA commands. The Protection and Balanced profiles honor FUA commands if no BBU is present; the Performance profile ignores them regardless of whether a BBU is present.

If you use a battery backup unit (BBU), FUA is ignored, because the BBU preserves the contents of the controller cache memory for a limited period of time (up to 72 hours), in the event of a power failure.

The above behavior is something just to be aware of in the "hot plug" world.

I have two Dell machines that use Intel drivers, but even then there is no ability to remove an installed SATA drive. So I will defer to Max and others with greater experience on this issue. I know what Max is saying (and what I inferred) can be done for USB/Firewire drives and is generally reliable, but was unaware that with some version/configuration of the Intel driver, any SATA drive can be treated as removable (and hence will flush the write cache, all the way through the stack, upon issuing 'stop').

ronrem · Post by **ronrem** » Tue Jul 31, 2007 2:12 am

alglove wrote:Hmmm, as I understand it, Skazka is talking about hot-unplugging the drives by going to the Windows system tray (down by the clock) and using the "Safely Stop/Remove a Device" icon. As I understand it, this makes going into the Device Manager and disabling all the write caching options unnecessary. That is the whole purpose of this icon.

I do not believe that Skazka literally meant "hot-unplugging", as in, "disconnecting the power from the drive without any warning". Of course, the SATA power plug is meant to support this safely, but on a data level, it is not safe, for all the reasons Tibetan mentioned.

Unfortunately, I do not have in particular insight into the Intel ICH7/ICH9 issue. The only chipsets I have used with SATA drives are the VIA KT880 (8327R southbridge, supports only "SATA-I") and the NVIDIA nForce Professional 3400. From my limited experience, "Safely Removing" the SATA drive seems to work fine with the VIA chipset (WinXP), but the NVIDIA chipset (Win2k3 server) does not seem to support it at all.

Bear in mind that I do not actually own an SATA drive at the moment, so my personal experience with both configurations is rather limited. Anybody with other experiences should surely feel free to add comments.

I wonder if there is some sort of way through the Windows power management to put the hard drive to "sleep" before "safely removing" it. I would think that it should be possible, at least in theory. I would guess that it may be easier in Vista, which has much more detailed control over the computer's power management.

The Safely Remove pretty much does put it to sleep. Works fine with my external-an IDE in a USB housing running off an old P-III system,and XP. Newer SATA drives are designed to "Hot Swap" better. Still--you obvoiusly don't just pull the plug in the middle of a seek or write.

I often boot up without the external on. Later-flipping the switch-turning it on seems to pose no problem. When the Puter is shut down-turning off the external is also no problem-though I tend to leave it on much of the time.

eSATA even lets the OS be on an external--you can have all drives outside the box,have storage on as needed.

Soon it will be cost effective to have a 16 mb SSD for the regular OS+ software,and have eSATA storage,maybe also secondary OS's at a distance of 6'

I could also see an acoustically planned homebuilt eSATA HDD case,using a low speed fan so you could even have a Raptor Raid run silent,in effect,by being well designed and further away.

Skazka · Post by **Skazka** » Wed Aug 01, 2007 11:51 am

I thank all of you for your inputs!

As I understood it is really safe to unplug the drive using "removable devices" in the System tray.
Has anyone had a problem with the system hang when using this option?

Skazka · Post by **Skazka** » Wed Aug 01, 2007 1:32 pm

Max Slowik wrote:This way is safe and supported by Microsoft, and I use it all the time with open test benches, since I don't have a personal file server set up yet, but I do have a big ol' stack of hard drives.

Did you use integrated on-board controllers or that were separate controllers such as: 3ware, marwell, areca...?

jackylman · Post by **jackylman** » Wed Aug 01, 2007 1:43 pm

I have had no problems using the "stop/disconnect" icon method on an integrated nForce4 chipset.

alglove · Post by **alglove** » Wed Aug 01, 2007 4:07 pm

jackylman wrote:I have had no problems using the "stop/disconnect" icon method on an integrated nForce4 chipset.

Thank you for mentioning that.

The NVIDIA chipset computer that I mentioned earlier was not my own, but one that I was repairing. It is possible that there was a driver issue or BIOS setting that prevented me from using this feature.