Sebastian et al are correct. You do not need to let deswizzling finish, but it is recommended that you do. Without deswizzling the destination volume, reads at the destination volume will be slightly slower (and slightly more expensive) as we do the PVBN -> VVBN lookups.
As Jeff said, the wafl_scan_speed setting is responsible for quite a few things -- not just deswizzling -- so it's best to use that at the behest of NGS.
Chris
From: <toasters-bounces@teaparty.netmailto:toasters-bounces@teaparty.net> on behalf of Sebastian Goetze <spgoetze@gmail.commailto:spgoetze@gmail.com> Date: Wednesday, June 24, 2015 at 5:05 AM To: Mike Michalakis <mike@directit.com.cymailto:mike@directit.com.cy>, Jeffrey Mohler <jmohler@yahoo-inc.commailto:jmohler@yahoo-inc.com> Cc: "toasters@teaparty.netmailto:toasters@teaparty.net" <toasters@teaparty.netmailto:toasters@teaparty.net> Subject: Re: Deswizzle
Hi Mike,
to simplify, deswizzling turns a two-way-lookup (-> logical block in volume -> physical block in aggregate) into a one-way-lookup. Read access to the destination volume will be slower (and more work for the controller) until deswizzling is done. If you don't access the destination volume, I don't foresee problems...
Sebastian
On 6/24/2015 10:36 AM, Tony Bar wrote: Jeff is right, let it run if you can. The option to disable it is so tempting, but you're better off just adding another shelf and running a reallocate.
On Jun 23, 2015, at 11:55 PM, Jeffrey Mohler <mailto:jmohler@yahoo-inc.comjmohler@yahoo-inc.commailto:jmohler@yahoo-inc.com> wrote:
This is normal, and -required- to...to simplify this, comb out the new physical to virtual block map required after a snapmirror update.
It will eventually finish, but if it never finishes, run a less intensive snapmirror schedule and let it catch up.
_________________________________ Jeff Mohlermailto:jmohler@yahoo-inc.com Tech Yahoo, Storage Architect, Principal (831)454-6712 TW: @PrincipalYahoo YM: Supra89ta
On Tuesday, June 23, 2015 11:51 PM, Mike Michalakis <mailto:mike@directit.com.cymike@directit.com.cymailto:mike@directit.com.cy> wrote:
Hi I have a storage system that is under stress, and as luck has it I need to added more stress by loading it with a large cifs related volume, this is a transition from a 7-Mode ontap system
Every time we complete the transition, the system spikes disks 100%, cpu 100%, etc. On the perfstat we see deswizzling running. This is a normal operation every time a snapmirror break-off occurs, that is the deswizzle part of the equation.. When we take this volume offline, operations go back to normal.
My question, what is the result of disabling deswizzle is the short term, do I look functionality, e.g. vol move?
To turn off deswizzle: Nodeshell*> options wafl.deswizzle.enable off To turn on deswizzle: Nodeshell*> options wafl.deswizzle.enable on
Backround: FAS3210, C-Dot 8.2.3, SAS disks
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