Or is this all wrong, and the access doesn't occur in blocks?
It does occur in blocks, and the WAFL block size is 4K bytes.
Steve
-----Original Message----- From: Edward Hibbert [mailto:EH@dataconnection.com] Sent: Wednesday, February 13, 2002 5:27 PM To: toasters@mathworks.com Subject: Block sizes
A question about block sizes on NetApp disks.
My impression is that disk access occurs in blocks. So if I write 1 byte to a disk, at some level the OS has a block in cache, updates the block, then writes that block out to disk. If I write 20K, then it probably affects multiple blocks.
If this is true, then it might be useful to know the underlying block size - because if I could ensure that my application wasn't spanning multiple blocks when I didn't need to be, I could give the physical disks a bit less of a hard time.
Does anyone know how to find this out? Or is this all wrong, and the access doesn't occur in blocks?
Thanks,
Edward.
Also worthy of note, to date there is no way to modify the block size. It's hardcoded in wafl.
~JK
"Strange, Steve" wrote:
Or is this all wrong, and the access doesn't occur in blocks?
It does occur in blocks, and the WAFL block size is 4K bytes.
Steve-----Original Message----- From: Edward Hibbert [mailto:EH@dataconnection.com] Sent: Wednesday, February 13, 2002 5:27 PM To: toasters@mathworks.com Subject: Block sizes
A question about block sizes on NetApp disks.
My impression is that disk access occurs in blocks. So if I write 1 byte to a disk, at some level the OS has a block in cache, updates the block, then writes that block out to disk. If I write 20K, then it probably affects multiple blocks.
If this is true, then it might be useful to know the underlying block size - because if I could ensure that my application wasn't spanning multiple blocks when I didn't need to be, I could give the physical disks a bit less of a hard time.
Does anyone know how to find this out? Or is this all wrong, and the access doesn't occur in blocks?
Thanks,
Edward.
Also worthy of note, to date there is no way to modify the block size. It's hardcoded in wafl.
~JK
While we're on the subject of WAFL trivia, WAFL does not split a 4K block into fragments, so files always consume disk space in even multiples of 4K bytes.
However, if the length of a file is 64 bytes or less, then the file data is stored in the inode and no data blocks are consumed. WAFL uses the space in the inode that otherwise holds the data block list.
This is nice because most symbolic links are small enough to fit in the inode.
Steve Losen scl@virginia.edu phone: 434-924-0640
University of Virginia ITC Unix Support
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Jeff Kennedy -
Steve Losen -
Strange, Steve