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From: Don jessup (djessup72, yahoo dot com) Date: 2001.11.08 - 13.45 MST
I believe all of this is explain in Chapter 12 of the Linux Device Drivers book 2nd Edition. --- Perry and Lorae Merritt <plmerritt, hypermall dot net> wrote: > I did some looking this morning starting at > /usr/src/linux/fs/buffer.c looking at the bread() > function. The bread function is the call in buffer > cache that either returns a hit or reads the data > from disk into cache and then returns the hit. It > calls a function called ll_rw_block which is in the > block drivers. It talks a bit about LVMs in that > code. Then a function called bh_present or > present_bh is called which then calles > generic_make_request. The last call, calls the > specific device driver for the device, presumably > ARVM. > > All through the call sequence a structure called > buffer_head is passed. It's defined in > /usr/linux/include/linux/fs.h and it contains the > block size, black address, dev number for the data. > > It looks like we can set the blocksize for our > device. It also looks like the default is 1KB, > giving a 4TB volume limit. > > That's about as far as I got. > > P > ----- Original Message ----- > From: June Mullins > To: antera, cryptofreak dot org > Sent: Wednesday, November 07, 2001 3:16 PM > Subject: Re: terabyte limit > > > Kevin's note says Reiser is limited by page cache > to 17592 GB on systems with 32 bit > addressing (presumably because Reiser uses 4k > blocks). Isn't that about 17TB, or am I misreading > the digits? And the LVM and block layer fixes, > which are below us, allow a logical volume > to be > 2TB, which it must be to accomodate the > larger file system. But I don't know what else > is involved. > > June > > > > > Perry and Lorae Merritt wrote: > > Since I'm pretty sure the block layer is below us > and since we're dealingwith physical devices that > are less than a TB, why would we apply fixes tothe > block layer?I guess what we really need to know is > how is LVM called from above? What isthe data > structure that is passed? I guess this is another > reason for me tohave a linux box here, or at least > the source code. ;-)In the old days, on AIX, the > block driver was passed a structure called abuf > structure. That structure had the device stuff in it > for the IO. Itcontained the mem address of where to > put/get the data, which device it wason, and the > offset on the device. Does Linux use a similar > mechanism?P----- Original Message -----From: "June > Mullins" <junemullins, earthlink dot net>To: > <antera, cryptofreak dot org>Sent: Tuesday, November 06, > 2001 2:09 PMSubject: Re: terabyte limit > So, from the note, it sounds like we would just have > to apply the 64 bitpatch tothe generic block layer > (and to lvm, if we wind up using it) to getaround > the 1 or2 Tb limit. However see the link in the > referenced note to the nextnote aboutLVM extent size > - that might be something to worry about if we use > lvmrather than roll our own. JuneDon > jessup wrote: > Here is a link to some information on the limit > size.http://lists.sistina.com/pipermail/linux-lvm/2001-September/008678.html__________________________________________________Do > You Yahoo!?Find a job, post your > resume.http://careers.yahoo.com--This ! > is the antera mailing list. To unsubscribe, > emailmajordomo, cryptofreak dot org with message body > `unsubscribe antera'.Or, for more information, visit > http://www.cryptofreak.org/. > --This is the antera mailing list. To unsubscribe, > emailmajordomo, cryptofreak dot org with message body > `unsubscribe antera'.Or, for more information, visit > http://www.cryptofreak.org/. > --This is the antera mailing list. To unsubscribe, > emailmajordomo, cryptofreak dot org with message body > `unsubscribe antera'.Or, for more information, visit > http://www.cryptofreak.org/. > > > __________________________________________________ Do You Yahoo!? Find a job, post your resume. http://careers.yahoo.com -- This is the antera mailing list. To unsubscribe, email majordomo, cryptofreak dot org with message body `unsubscribe antera'. Or, for more information, visit http://www.cryptofreak.org/.
This archive was generated by hypermail 2b30 : 2001.11.09 - 04.02 MST |
