more than one sata drive is unstable

[aep]

when attaching 2 identical drives, sda times out.
both drives work fine when running alone.

same behaviour on CEX rev 1.7 and 2.0 with clearfog itx 1.2

[    9.366518] ata2: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
[    9.372964] ata2.00: supports DRM functions and may not be fully accessible
[   14.522519] ata2.00: qc timeout (cmd 0x2f)
[   14.526628] ata2.00: ATA Identify Device Log not supported
[   14.532124] ata2.00: Security Log not supported
[   14.536655] ata2.00: failed to set xfermode (err_mask=0x40)
[   14.542225] ata2: limiting SATA link speed to 3.0 Gbps
[   14.547356] ata2.00: limiting speed to UDMA/133:PIO3
[   15.026546] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   15.032764] ata2.00: failed to IDENTIFY (I/O error, err_mask=0x100)
[   15.039029] ata2.00: revalidation failed (errno=-5)
[   15.043903] ata2.00: disabled
[   15.522521] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   16.002520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   16.482520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   16.962520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   17.442520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   17.922520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   18.402520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   18.882516] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   19.362521] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   19.842520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   20.322520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   20.802520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   21.282500] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   21.762521] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   22.242519] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   22.722520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   23.202520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   23.682520] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
[   74.986527] ata3.00: exception Emask 0x0 SAct 0x2000 SErr 0x180000 action 0x6 frozen
[   74.994281] ata3: SError: { 10B8B Dispar }
[   74.998384] ata3.00: failed command: READ FPDMA QUEUED
[   75.003540] ata3.00: cmd 60/08:68:20:6a:70/00:00:74:00:00/40 tag 13 ncq dma 4096 in
[   75.003540]          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[   75.018594] ata3.00: status: { DRDY }
[   75.498576] ata3.00: revalidation failed (errno=-5)
[   81.046578] ata3.00: revalidation failed (errno=-5)
[   86.678573] ata3.00: revalidation failed (errno=-5)
[   87.158584] blk_update_request: I/O error, dev sda, sector 1953524256 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
[   88.598597] blk_update_request: I/O error, dev sda, sector 1953524256 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[   88.609208] Buffer I/O error on dev sda, logical block 244190532, async page read
[   92.894545] ata2: EH pending after 5 tries, giving up

[justizin]

Having similar problems about 18mo later, frustratingly... I'm trying to build a SATA raid with four identical SSDs, I can almost never see all four, and I get lots of similar dmesg entries to above.

This is one of the more severe, but certainly not the only, reasons I'm looking at building a custom kernel.

I honestly upgraded a quad of older drives which were Fast Enough(tm) for my needs because I worried they were too old of SATA or something, but same issue.