Whats a decent amount of free space in regards to this?
80%? 85%? 90%?
Also are we talking about at the volume level, or aggregate level?
Just to clarify :)
Hadrian Baron Network Engineer VEGAS.com
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Stephen C. Losen Sent: Friday, July 14, 2006 5:43 AM To: margesimpson@hushmail.com Cc: toasters@mathworks.com Subject: Re: Defragmenation Question on Filer after few GB deletion.
Hi all: Could tech gurus respond to this question: I am planning to clean up some space on the filer - say 10GB.
Since WAFL FS is intellegent minimizing the defrag issues, what happens on deletion of the files on my volume? If I delete 10GB of 50GB, will the FS still be fragmented, or WAFL does it auto when files are deleted? Do I will have to run defrag tools explicitly?
Thank you for your reply. Marge.
I don't think you will have any performance problems and I don't think that you will need to run any tools to reorganize the disk storage. Freeing disk space does not increase "fragmentation" in WAFL.
The way WAFL is designed, if you have a decent amount of free space then WAFL is able to write data efficiently and hence read it back later efficiently. If you have enough free blocks, then WAFL can localize a disk writing episode to a small number of RAID stripes, which is more efficient than scattering writes over many RAID stripes, because WAFL must update the parity for each RAID stripe that is changed. Note that each block in a RAID stripe is on a different disk, so writing a RAID stripe writes to numerous disks in parallel.
Where you run into trouble is when you let an aggregate or traditional volume get nearly full. This means that free blocks are scarce and so WAFL must make do with whatever free blocks it can find. The free blocks may be scattered over many RAID stripes, which requires many more parity updates. This can also hurt read performance later when you want to read the data back (even though parity is not an issue when reading).
Freeing up disk space should improve your write performance and not hurt your read performance.
Steve Losen scl@virginia.edu phone: 434-924-0640
University of Virginia ITC Unix Support