Tapio
1 Copper

Aggressive Storage Tiering

We are having slight performance problems with our SC4020. Performance is adequate on normal operations, but full -backups takes too much time.

We  have two tiers, SSD and 7k HDD. We are considering buying more SSD-capacity to speed things up, but I'm not sure if this is good idea because system is using only maybe 20% of SSD-capacity. 

For me, it seems that Compellent is tiering data from SSD-disk too aggressively. Is there any settings to control how much data is kept on SSD-disks?

0 Kudos
1 Reply
BVienneau
3 Argentium

RE: Aggressive Storage Tiering

If the data is cold/untouched it will auto-tier down to the 7K. Backups hit all data, no matter where it's stored in ssd or 7k. My guess is that the 7K tier was designed to dense and the 7K drives cannot keep up with the demand of the backups but "normal" IO the data goes untouched or rarely touched so it can meet the demand.  

You can change your Storage Policies to keep some data in only SSD if you want, but you cannot change the algorithm used for when it wants to tier something down to 7K.  If you are only using 20% of SSD, then tell your higher IO/more important stuff to stay up in SSD.