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Forum Discussion
BTRFS, Sync Writes, and performance
Hello, Prior to OS 6, with the ext4/LVM file system, the ReadyNAS had a simple option to disable write caching (in System/Performance of RAIDiator 4.2.31, for example). When you did that, you co...
I have an older ReadyNas Ultra 6 that is still running 4.2.28 I believe and the write caching won't affect any write caching built-in on the drives (which on today's drives are typically using nvram to essentially have a micro ssd for the cache in case of a power outage). But I believe it does change how the ram is used as I think I recall the write speed changing in my speed tests when evauluating the unit.
SamirD wrote:
I have an older ReadyNas Ultra 6 that is still running 4.2.28 I believe and the write caching won't affect any write caching built-in on the drives (which on today's drives are typically using nvram to essentially have a micro ssd for the cache in case of a power outage). But I believe it does change how the ram is used as I think I recall the write speed changing in my speed tests when evauluating the unit.
My Pro-6 is still on 4.2.31, and that is my impression also.
This is easy to check on OS-6, as smartctl will tell you.
# smartctl -x /dev/sda | grep -i cache Write cache is: Enabled Wt Cache Reorder: Enabled
#
But the older version of smartctl on OS 4 systems does not.
PRO:~# smartctl -x /dev/sda | grep -i cache PRO:~#
To the main question: I don't use iSCSI, but my understanding is that the performance issue you are seeing isn't unique to ReadyNAS (or BTRFS). I've seen similar posts on FreeNAS using ZFS.
It's possible that using metadata tiering would help. Or I guess leave it disabled, and make sure the NAS is UPS protected.
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