Just jumped in to this thread, hope I am following it ok.
My F880 fits the scenario I think. We have had multiple volumes over 80%, one of them hitting 90% occasionally. These are reasonably busy disks, during peak times utilization hits 60-80% on the Sybase db volumes and may be 40-60% on the batch volumes. The only time we noticed a significant performance drop was when our db volumes were at around 85-90%. They ran like that for a month at least with utilization at 100% and cache age <5ms. The wafl scan measure_layout never went above ~3, indicating defragmentation was never an issue. The batch volumes at 90+ % were similar.
The db volumes were fixed by adding a shelf of disks to each. Good old-fashioned write bottlenecking being the culprit.
Not sure if that helps.
Aaron www.navitaire.com
-----Original Message----- From: Frank Marxs [mailto:fmarxs@mail.com] Sent: Wednesday, February 26, 2003 8:40 AM To: Deepak Soneji Cc: toasters@mathworks.com Subject: Re: Fragmentation
Deepak,
Filers get fragmented over time ... I guess that's just the basic drawback of having a 'Write Anywhere File Layout'.
One one hand I've been told the WAFL is designed to handle Fragmentation but then I'm told to run 'scan' on the filesystem periodically if I'm anywhere near capacity. [I'd say most people don't run their filers empty ... unless they're new ... but over time the filesystem approaches capacity and Fragmentation sets in] ... and I am also told never to add a single drive because that increases fragmentation [all the new data gets written to the new drive if your other drives are full, creates a hot disk for your new files, and your old files get a few new blocks on the new drive ... it'll take a while for the load to balance itself out, if it ever does.]
I've just resigned myself that Fragmentation over time is a fact of life, you add a full shelf at a time, and hope the users dont notice or complain about degrading performance over time... If I upgrade my filers yearly they shouldn't have time to get fragmented anyway...
My guess is that most users run evaluation or benchmarks on a new, empty [i.e. unfragmented filer]. I'd be curious to see what the Spec FS or other benchmark performance is on a filer which has been in production for 6 months with a filesystem which is 80% full ... then have someone tell me that Fragmentation doesn't make a difference.
Cheers Frank
"Anyone who has never made a mistake has never tried anything new." - Albert Einstein
----- Original Message ----- From: "Deepak Soneji" sonejideepak@hotmail.com Date: Mon, 24 Feb 2003 12:46:18 -0800 To: toasters@mathworks.com Subject: Fragmentation
Hi
We have FAS960 filer running ONTAP Release 6.3.1. I have heard that over the period of time the performance of filer decreases as it is
getting
more fragmented.
How do I check fragmentation ? How can I defrag ...any scheduled job or internal utility ? How can I minimize fragmentation and monitor it ?
Thanks /Deepak