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Mirror Write Speed
Posted: Wed Jun 08, 2011 4:33 pm
by chop
Feel quite foolish, we bought the Mirror and Replication edition to do the following:
Server - ISCSI Target Host - Replication ISCSI Target Host
The replication was going to occur over 100mbs link to another campus. The problem we have is really poor write speed to the primary ISCSI Target, we have enabled async, caches on both sides. But it is still alot slower then a normal .img disk.
Is there anything that can be done, other then switch off the mirror and buy into something else!!!
Re: Mirror Write Speed
Posted: Wed Jun 08, 2011 4:40 pm
by Max (staff)
Hi chop,
What are the current modes for primary and secondary mirrors?
Have you tried to do some network tuning between the machines?
Re: Mirror Write Speed
Posted: Wed Jun 08, 2011 4:49 pm
by chop
Modes? I just created the mirror as stated somewhere in the forum and they are linked by a 1GBE vlan in async config.
First Mirror: write thru 2048mb cache
Second Mirror: normal no cache (have tried so many times to turn caching on at this point). When the mirror was created is was created with the same write thru cache config.
Re: Mirror Write Speed
Posted: Wed Jun 08, 2011 4:58 pm
by chop
ATTO test
Mirror Enabled

- Untitled-3.gif (17.09 KiB) Viewed 7495 times
No Mirror Enabled

- Untitled-4.gif (15.43 KiB) Viewed 7484 times
Re: Mirror Write Speed
Posted: Wed Jun 08, 2011 7:55 pm
by Max (staff)
What is the cache size you use on the primary host? and what is the cache mode you've set for the second mirror (not the image but the target you're selecting in the wizard when creating the mirror device)
Try to set the second mirror to Replication mode, this should increase the write performance, also the cache should be at least 128MBâ™
Re: Mirror Write Speed
Posted: Wed Jun 08, 2011 8:24 pm
by chop
Primary Cache: 2048
Secondary Cache: 2048
Secondary Cache Target: 2048
Tried to set it to replication and when I check the settings after the mirror is created it always says Normal (No Caching)!!!
Re: Mirror Write Speed
Posted: Thu Jun 09, 2011 8:19 pm
by Max (staff)
That's strange, I can not reproduce this, the GUI does really show no caching, but the writes are about 60 MB/s and reads are @ 80-90 in an old demo lab. I think it's something with the allignment here...