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- Path: mail2news.demon.co.uk!harden.demon.co.uk
- From: Mark Harden <mark@harden.demon.co.uk>
- Newsgroups: comp.sys.amiga.applications
- Subject: Re: Problems with AFS - Any Help?
- Date: Sat, 16 Mar 96 14:29:10 GMT
- Organization: Private Node
- Message-ID: <9603161429.AA0021l@harden.demon.co.uk>
- References: <Pine.SUN.3.91.960315192733.25955C-100000@osiris>
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-
- STEVEN KELLS (sis3538@sis.port.ac.uk) wrote:
- :
- : When I run the ValidDisk from AFS-Pro (15.9) it says "block xxxxx allocated
- : but not used" (hundreds of times) and reports this as an error.
- : So I ran the FixDisk and that seemed to sort out all the errors.
- : But after a short time they all build up again and occasionally I`ll even
- : get a "Directory not valid" which I have found no way of getting back (even
- : through DiskSalv 4).
- :
- : It seems that when I use DirectoryOpus 4 or the Zip drive these errors
- : happen, but I`m not too sure.
- :
- : The only other thing I can think of what could be the culprit is the DMA
- : mask, set in HDToolBox, my Hard Disk has the same value as the Zip Drive
- : (using Squirrel).
- :
- : Do they have to be different? If so what is the correct hex number?
- : (They are both at their defaults 0xfffffffe)
-
- Have you tried FLD on support@flevel.co.uk ?
-
- The Block allocate and not used problems with 15.9 are well known and the
- fix mode of DiskValid fixes it well. The other problem is more serious.
-
- I am the author of the AFS FAQ and I attach the sections on MaxTransfer and
- DMAMask for you to check. If this doesn't help get in touch with FLD at the
- above email address. They will probably help...
-
- Please do not distribute this snippet of the FAQ. A new revised version will
- be available at the beginning of April....
-
- 23. What is MaxTransfer ?
-
- Some IDE drives have problems with high MaxTransfer values, they seem
- to "choke" on large blocks of data if they are sent by the controller
- in one gulp. SCSI drives should run with any MaxTransfer, I haven't
- had any problems with them.
-
- By the way, the MaxTransfer value is hardly important for the disk
- performance - a value of 0xFFFFFF means "16MB max in one transfer"
- while a value of 0xFFFF is still 64K. I once set it as low as 2K and
- the loss of speed was hardly noticable.
-
-
- 24. What value should MaxTransfer be ?
-
- IDE Drives - Try 0x1FE00. If files greater than 64K get corrupted
- then reduce it to 0xFE00.
-
- SCSI Drives - Use 0xFFFE00.
-
- It must also be divisable by the sector size (512) due to a bug in the
- WorkBench format code.
-
-
- 25. What is DMAMask ?
-
- DMAMask is used for two purposes :-
-
- 1. High speed devices like disk controllers can read data straight
- from memory without any CPU load. This access is call direct
- memory access or DMA.
-
- Standard Amiga devices can only use CHIP memory for DMA. Disk
- controllers are usually capable of using DMA to any memory.
-
- The DMAMask value restricts DMA activity by a particular device
- driver to a particular area of memory.
-
- The default value of 0xFFFFFF restricts DMA to the Z2 area. This
- is a bad idea for any Z3 based machine which always has memory
- outside this area. In this case 0xFFFFFFFC would be a better
- value.
-
- 2. The DMAMask also control the alignment of any buffers used to
- access the device. The least significant bits are used to control
- this. Values with no zero bits, end in 0xF, will have no
- alignment. Values with one zero bit, end in 0xE, will be word
- aligned. Values with two zero bits, end in 0xC, will be long word
- aligned.
-
- The alignment can make a lot of difference to performance.
- Longword alignment is usually the best.
-
-
- 26. What value should DMAMask be ?
-
- Read the instructions that came with your computer or disk controller.
-
- If this doesn't help look at your memory map with ShowConfig. Use the
- maximum memory address as a starting point. This should have a number
- of F's in it. Change the last F to a C to ensure longword alignment.
- Use this value.
-
-
- 27. How many buffers should I assign to each AFS partition ?
-
- The HDToolBox default of 30 buffers, actually 50, will result in poor
- performance. The minimum should be 100. If you have the memory use
- 200 buffers for active partitions.
-
- Remember that each buffer is 1024 bytes and NOT 512 as is true for
- FFS.
-
- AFS sanity checks the number of buffers ensuring that the value is
- between 50 and 300.
-
- --
- Mark Harde
-