just in case it will be useful to somebody - here is my checklist for
better read performance from SSD
1. limit read-ahead to 16 or 32
2. enable 'trickle_fsync' (available starting from cassandra 1.1.x)
3. use 'deadline' io-scheduler (much more important for rotational
drives then for SSD)
4. format data partition starting on 2048 sector boundary
5. use ext4 with noatime,nodiratime,discard mount options
On 05/16/2013 10:48 PM, Edward Capriolo wrote:
I was going to say something similar I feel like the SSD drives read
much "more" then the standard drive. Read Ahead/arge sectors could and
probably does explain it.
On Thu, May 16, 2013 at 3:43 PM, Bryan Talbot <[email protected]
<mailto:[email protected]>> wrote:
512 sectors for read-ahead. Are your new fancy SSD drives using
large sectors? If your read-ahead is really reading 512 x 4KB per
random IO, then that 2 MB per read seems like a lot of extra overhead.
-Bryan
On Thu, May 16, 2013 at 12:35 PM, Keith Wright
<[email protected] <mailto:[email protected]>> wrote:
We actually have it set to 512. I have tried decreasing my
SSTable size to 5 MB and changing the chunk size to 8 kb
From: Igor <[email protected] <mailto:[email protected]>>
Reply-To: "[email protected]
<mailto:[email protected]>" <[email protected]
<mailto:[email protected]>>
Date: Thursday, May 16, 2013 1:55 PM
To: "[email protected]
<mailto:[email protected]>" <[email protected]
<mailto:[email protected]>>
Subject: Re: SSTable size versus read performance
My 5 cents: I'd check blockdev --getra for data drives - too
high values for readahead (default to 256 for debian) can hurt
read performance.
