Today, copied from someone's posts to IRC for MacZFS –
> copying data feels slow, but it doesn't seem like it's hanging on every access
– and:
- Code: Select all
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
Media2 1.82T 1.79T 30.0G 98% ONLINE -
That 98% is way beyond the
eighty that I'd recommend, the user plans to add a disk to the pool.
----
Yesterday, I was pleasantly surprised by
better than expected performance from an extremely full disk (usually between 96% and 99% full at the pool level, 2 TB, much like the one discussed in IRC). In screenshots there, the 15.98 MB/s peak is way below what I'd expect from a
sanely used drive of its class – Seagate GoFlex Desk – but for many datasets in this pool (at this stage in development of ZEVO) I'm happy to combine alarmingly little free space with rarely-recommended
compression=gzip-9 – use of the pool for anything other than backup is so rare that I don't care about performance.
To the point of this post: the peak and averages, during yesterday's backup session, were dramatically
greater what I had learnt to expect from use of the pool in recent weeks. Averages were probably more than one hundred times greater.
Without giving too much thought, I couldn't find an explanation for the greater performance yesterday. I wondered whether the data backed up lent itself more easily to gzip-9 but glancing at the log (two backups and a review of holds on a snapshot.txt), the stream sizes were typical so I assume that stream content was typical.