How hard links work

re: How hard links work

Robert Mitchell [MSFT] — Tue, 10 Jan 2012 23:41:24 GMT

I did do a part 2 for this. Here's a link to the second posting.

blogs.technet.com/.../more-on-hard-links.aspx

re: How hard links work

joscon [Microsoft] — Tue, 07 Jun 2011 18:17:44 GMT

Dean;

I actually havent forgotten about it but I've just been really busy for the last couple of months. I'll speak to Rob today and see what he thinks on a time line.

--Joseph

re: How hard links work

Dean — Tue, 07 Jun 2011 18:14:58 GMT

Joseph,

Is there any chance that you will be able to do the better document yet ?

re: How hard links work

joscon [Microsoft] — Thu, 21 Apr 2011 13:47:41 GMT

@Aaron; Hardlinks are very efficient actually. Explorer reporting the space usage is documented above and on other Windows blogs. It's not an issue because explorer needs to treat them all as physical files in the event that all but one link is removed from the file. I dont know what your component store usage is on your systems but if its under 15GB then it would be considered normal.

re: How hard links work

Aaron — Thu, 21 Apr 2011 12:43:22 GMT

@joscon Hi and thanks for your responses. Does this mean that Explorer is reporting correctly the disk is full when much of the drive space is only being used by hard links? This makes no sense to me. What is the point of a hard link versus just saving multiple copies of the actual files. There's no efficiency in the model Microsoft chose whatsoever if I understand you correctly. I'm trying to combat my disks constantly filling up sending me Nagios alerts and using up very costly SAN space. Please advise as I am constantly battling Windows 2008 filling up the C drive with WinSXS and other hard linked files.

re: How hard links work

joscon [Microsoft] — Mon, 04 Apr 2011 10:47:06 GMT

@Ikraav; Hard links provide the ability to update a file in multiple locations by using just one instance of a file, it's a common file system efficiency model. It wasnt used to get the OS "out the door" at all. From a servicing perspective, it actually provides a very useful function and that's during repair operations. Just the other day we had a customer that had a server down because of some unknown software installation failure. It turned out that the software they were installing was trying to forcefully attempt to overwrite a system binary and was partly successful. Because of hardlinking, we were able to run SFC against the file and get the machine back up in a couple of seconds.

re: How hard links work

lkraav — Sun, 03 Apr 2011 14:56:38 GMT

@joscon: thanks a lot for clarification.

so in other words while hard links as a concept is designed for space efficiency, in this windows vista+ ecosystem implementation all the hard links might as well be actual space occupying files, since the the space is unusable for the user anyway.

is there *anything* the user wins out of this hard links winsxs implementation vs regular files? was this implementation acceptable because the initial product needed to get out the door and making the hard linked saved space actually available for use could be addressed with some patch in a later service pack (obviously not in W7SP1..)?

re: How hard links work

joscon [Microsoft] — Sun, 03 Apr 2011 10:16:05 GMT

@Ikraav; RIght now nothing is very accurate when it comes to the actual size reporting of the directory. I've had talks around a better tool internally so we'll see what comes out of it. As for your question about copying extra data to the drive, the answer is no. Once explorer see's the disk as full, its full.

re: How hard links work

lkraav — Fri, 01 Apr 2011 21:28:33 GMT

Hi joscon, thanks a lot for your writings on the subject.

(W7 SP1) With regards to WinSxS, hard links and Windows Explorer not being able to calculate this folder's real size correctly, I'm wondering where am I supposed to get my accurate Drive Free Space reading from? If Explorer can't account for hard links, can any other built-in Windows tool (Disk Mgmt, anything else)? Or does this mean that drive free space is constantly reported incorrectly? What happens if Explorer thinks WinSxS occupies 15G, when physically it occupies only 1G, and I fill the disk up? Will I be able to copy 14G more files on the drive with the free space indicator staying at zero all the time?

re: How hard links work

joscon [Microsoft] — Sun, 13 Feb 2011 11:42:27 GMT

Dean;

I haven forgotten about it but the release of SP1 has me pretty busy atm. I'll see what I can do in regards to a better image for you and post something as soon as I have it.

--Joseph