How To Implement A Database Oriented File System

ALundi writes "A really great read from Andrew Orlowski over at The Register on how Benoit Schillings and Dominic Giampaolo created the 64-bit journaled and attribute based Be File System. Schillings and Giampaolo discuss a variety of design and implementation issues, including data integrity and file system performance. " Interesting in the context of MSFTs plans to implement a DB filesystem in future versions of MS Windows.

Comments

BeOS file system rocks.

[morgajel]

I used Be on and off for about 6 months. Once you get the hang of it(the filesystem), you see the true power- especially with the address book.
If you want some real insights into the OS as a whole, check out the BEOS Bible. not so good if you want an in depth discussion, but for non-kernel hackers it's a fun read and very informative.
Read the section explaining how their address book works. it's really cool.

Re:wrong way round

[JordanH]

• for the majority of databases the data should be moved to the filesystem no the database.

  Simple joins, and most of them are can be replicated with links if necessary. Almost all the databases I've seen would lose little from moving out of the DB and into the filesystem.

But then, you lose all the advantages of database journaling (not just integrity, the ability to rollback to a previous state, if necessary), consistency (you have to make sure the files can't be accessed by other operations before the commits are done) and replication.

If I were building an application today with Oracle, I would be very tempted to use iFS for these reasons.

Leveraging a DB FS

[bihoy]

One of the areas that I am interested in is using a DB FS with various "helper" apps. These helper apps would provide a way of managing your data. They could be integrated into another app directly or as a plugin or they could be standalone apps by themselves.

One could provide a helper app that allows you to look at the stored files in ways other than your typical file listing. To do this would require various metadata attributes to be associated with the data. Helper apps would be provided for all of the standard applications that read and write to data to the file.

For example, one app could set attributes to categorize data. One could then search for data on your system, and potentially others, much in the same way as you would search for stuff on Yahoo.

Say you are in a rush to finish your taxes but you need to put together an itemized list of business expenses. You have information on them stored in various places including text files, e-mail, spreadsheets, etc. You could use find and grep to go poking around looking for them or you could use a helper app that does a quick search of attributes and presents you with a list of candidates and ca even call up other apps or services to look at the data. Once you have identified the data another attribute can be set that your tax software uses to record it and pull it into your tax forms.

Microsoft is NOT putting SQL Server into Windows!!

[Anonymous Coward]

I should know - I actually interviewed for a position in the group developing this. (I signed the standard pre-interview NDA, so I'm posting anonymously, but I'll still try to stay general so I don't get into too much trouble...)

As the ExtremeTech article pointed out, they are not even considering putting the full-blown SQL Server into Windows. SQL Server is too resource-intensive (it really wants to use all of the available CPU, memory and disk space), too much overhead, and most importantly to MS, too profitable (sales of SQL Server / BackOffice make up about 10-15% of MS's revenue.) There's no reason to bundle it if people are willing to pay a ton for it separately!

As the article says, they're thinking (nothing decided yet) about including MSDE, which is exactly the same as SQL Server 2000, except it is tuned for 5 concurrent users (and hard-limited to 10), the database size is limited to 2GB per database (the same as the Jet DB, aka Access), and it doesn't have the nice GUI admin tools bundled.

Also, the OFS (Object File System) discussed previously probably won't get added either. There's a good reason why it was talked about way back in the Cairo (pre-Win95) days but never implemented - it's really, really hard to do, and it's hard to even convince anybody of its value. (Just look at Be.) Active Directory was originally supposed to be an object store, but I don't think anybody uses it for that (if anybody even uses it at all.)

What probably will be included is an improved version of Indexing Service, which is currently included in Windows 2000 and XP. For those of who are fortunate enough to be unfamiliar with Indexing Service (formerly Index Server), it's an NT service (think "daemon") that periodically scans the file system for new / updated files, and then adds whatever metadata it can extract into a database of sorts, which is then used to speed up searches in the built-in Search dialog on the Start menu.
There are a couple of problems with the current implementation:

1. It's extremely buggy. For example, it's supposed to run only when the system is idle, but it usually chooses to run right when I'm doing some big IO-intensive process. It periodically also consumes all available memory and CPU cycles, so I usually leave it turned off.
2. It doesn't index very much metadata. For most files, it only indexes the standard file system attributes (size, date, extension, etc.) For MS Office documents, it can index the Summary Information property stream, which usually includes things like Author, Title, etc. If you have IIS running on a box, it can also index the META tags in HTML documents. Other than that, not much. It does have some extensibility , by means of DLLs that implement the IFilter COM interface, but no 3rd-party vendor seems to have done much with that, perhaps because of #1.

So, in summary, MS's plans for the DB-in-the-filesystem look a lot more like Reiser4 than like BeFS or SQL Server.