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How to get write-aside value on Pool LUNs?
I know that this discussion has already taken place:
I know that that answer says that the write-aside size is the same as a default LUN, 1MB and higher (inclusive). But that answer isn't helping me for a few reasons.
1) The answer is a few years old. What if the answer has changed in subsequent code versions?
2) I created a traditional LUN. It's write-aside size from the CLI is also zero (IP omitted for obvious reasons):
naviseccli -h w.x.y.z getlun 4 |findstr "RAID Aside"
RAID Type: RAID5
RAIDGroup ID: 7
Write Aside Size: 0
3) Is there some way to determine this answer myself without resorting to posting to EMC forums?
Anonymous
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February 22nd, 2016 02:00
Hi,
1. On Flare Release 32 and lower default Write-Aside value is 1 MB (2048 blocks)
2. Starting from Flare 33 default Write-Aside Value is 0 so everything pass trough Cache
ghahn1
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February 22nd, 2016 13:00
Are you saying ALL LUNs go through cache starting at Flare 33? That write-aside is essentially gone and all LUNs, whether traditional or pool, go through cache?
Do you have some documentation to show that? I've seen replies on this very forum that say the opposite of that (also without documentation to show it).
Thanks,
Greg
Anonymous
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February 23rd, 2016 06:00
Yes correct, as default MCx write-aside is set to 0 so everything is cached and mirrored via CMI, but you can set the write-aside on every single luns and here there is a write-aside performance test results.
ghahn1
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February 23rd, 2016 12:00
I'm not sure what document you're referencing, but please re-read the original question. The question is about the write-aside on POOL LUNs, not Classic R5 LUNs, as referenced in your pictures.
In addition, the command referenced in your email doesn't work, at least not for POOL LUNs:
Error: chglun command failed
Switch not supported: -w
One or more of the specified switches is not supported for the input Pool lun.
Anonymous
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February 24th, 2016 23:00
Hello Ghahn, confirmed that cannot set write-aside on Pool Luns, just Classic Luns.
You cannot as well change private Pool Luns write-aside value.
Check out as well this post:
https://community.emc.com/message/562495