I've done some logs indexing benchmark with Solr with Redhat 7.3.
The machine included 2 7200 RPM with software RAID 1, 64GB memory and a E3-1240v6 CPU.
I was really surprised to find a huge difference in IO performance between ext4 and xfs (see details below).
Indexing with xfs provided 20% more indexing throughput compared to ext4 (io wait is tenth with xfs).
I'm looking for some insights related to choosing the appropriate file system for a Solr machine.
ext4:
avg-cpu: %user %nice %system %iowait %steal %idle
3.09 62.43 1.84 14.51 0.00 18.12
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdb 0.02 169.38 13.95 182.97 0.36 26.28 277.04 40.91 207.66 18.96 222.05 3.82 75.18
sda 0.04 169.34 20.55 183.01 0.61 26.28 270.51 47.18 231.71 27.84 254.60 3.76 76.51
xfs:
avg-cpu: %user %nice %system %iowait %steal %idle
3.18 81.72 2.19 1.48 0.00 11.42
Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sda 0.00 17.51 0.00 123.70 0.00 29.13 482.35 34.03 274.97 56.12 274.97 5.39 66.63
sdb 0.00 17.53 0.09 123.69 0.00 29.13 482.05 34.84 281.29 25.58 281.48 5.29 65.52
as you have done the testing yourself (hopefully similar to your intended production usage), nobody else will have better advise regarding the FS. Of course, if you could change the spinning disks for SSD, that would be much, much better, specially for indexing througput.