Varnish on SSD

Anand Shah anand at
Mon Aug 9 09:16:53 CEST 2010

Hi Guys,


This is my first post on mailing list and would like to have your
suggestions on this. 



I'm contemplating setting up a varnish cache on a system with SSD drives.


The obvious benefit is that these systems have great READ speeds and I
expect my hit ratios to be fairly high.


Let's assume I can put 7 SSDs in to a RAID configuration. (there are some
cases that will let me pack in much much more)


Implementation questions:


Should I use RAID0? (I expect a drive to fail eventually, so this seems


Should I use RAID10? (This halves my disk footprint, which is costly.)


Should I use RAID5? (SSDs are known to have "bad" write performance and
write limits, and all the extra parity writes may slow this down


Should I just treat each disk as it's own squid datastore? (how well does
squid handle multiple data stores? and what happens if/when one fails?)


Should I ignore datastores and just make the SSDs in to large SWAP
partitions and let the linux VM do it's thing? (seems sloppy)


Any advice from you using SSDs in production environments would be greatly
appreciated. (esp if you're using them for HTTP caches)


Also how difficult it is for a varnish cache to allow users manage data life
cycle policy from SSD/NAND flash drives to disk. There is an open source
project on Online Hierarchical Storage Manager (OHSM) (e.g.  which i am on verge of trying bt havent
succeeded yet.



Awaiting for your reply on this!!!!






   Anand Shah

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