Understanding ASHIFT SSD and adding a mirrored vdev
Michael Jung
mikej at mikej.com
Thu May 15 13:35:00 UTC 2014
On , Steven Hartland wrote:
> ----- Original Message ----- From: "Michael Jung" <mikej at mikej.com>
> To: <freebsd-fs at freebsd.org>
> Sent: Thursday, May 15, 2014 1:14 PM
> Subject: Understanding ASHIFT SSD and adding a mirrored vdev
>
>
>> Hi:
>>
>> I have read so many threads about ASHIFT on SSD my head is spinning.
>> This is my current partition created with a 10-stable installer. 2x3TB
>> drives in mirror and ashift=12 looks correct. I added the SSD
>> which defaulted to ashift=9 and this is where my question is.
>>
>> Is alignment on SSD important as from what I read we never really know
>> the flash layout? I hope there is a simply answer to this ;-)
>
> SSD's are generally 4K devices yes, but they also almost always lie
> about their 4k ness, instead reporting 512byte sectors for max
> compatibility.
>
> To work around devices which lie FreeBSD has device "quirks", we've
> included 4k quirks for quite a large number of SSD's but the list is
> ever growning so its not garanteed that your SSD will have a quirk
> to correct its lies, if in fact it is lieing.
>
>> Secondly, I want to add another vdev 2x mirrored 3tb drives and it
>> seems that ashift would be vdev specific so I would need to gnop the
>> new
>> drives before add the new vdev?
>
> I've just MFC'ed r264850 to 10-stable, seems I forgot to tag with MFC
> so
> didn't get a reminder, so if you update to the latest source you'll
> have
> a new sysctl: vfs.zfs.min_auto_ashift
>
> This can be used to force the ashift to be artificually increased,
> which
> is useful for forward compatibility.
>
>> <gnop magic to create partition and set ashift=12>
>
> Instead use: sysctl vfs.zfs.min_auto_ashift=12
>
>> then
>>
>> zfs add zroot mirror ada3 ada4
>
> Also what is your SSD can you provide the details from:
> camcontrol identify ada2
>
> This will allow us to create a new quirk if needed.
>
> Regards
> Steve
Steve thanks for you quick reply, and I'm updating now. Here are two
different SSD,
they both claim to 512 bytes logically and physically.
root at charon:/usr/home/mikej # camcontrol identify ada1
pass2: <Samsung SSD 840 PRO Series DXM05B0Q> ATA-9 SATA 3.x device
pass2: 600.000MB/s transfers (SATA 3.x, UDMA6, PIO 8192bytes)
protocol ATA/ATAPI-9 SATA 3.x
device model Samsung SSD 840 PRO Series
firmware revision DXM05B0Q
serial number S1ANNSAD905507F
WWN 50025385a00fff63
cylinders 16383
heads 16
sectors/track 63
sector size logical 512, physical 512, offset 0
LBA supported 250069680 sectors
LBA48 supported 250069680 sectors
PIO supported PIO4
DMA supported WDMA2 UDMA6
media RPM non-rotating
Feature Support Enabled Value Vendor
read ahead yes yes
write cache yes yes
flush cache yes yes
overlap no
Tagged Command Queuing (TCQ) no no
Native Command Queuing (NCQ) yes 32 tags
SMART yes yes
microcode download yes yes
security yes no
power management yes yes
advanced power management no no
automatic acoustic management no no
media status notification no no
power-up in Standby no no
write-read-verify yes no 0/0x0
unload no no
free-fall no no
Data Set Management (DSM/TRIM) yes
DSM - max 512byte blocks yes 8
DSM - deterministic read yes zeroed
Host Protected Area (HPA) yes no 250069680/250069680
HPA - Security no
root at charon:/usr/home/mikej #
root at firewall:/home/mikej # camcontrol identify ada2
pass2: <CT128V4SSD2 S5FAMM25> ATA-8 SATA 2.x device
pass2: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes)
protocol ATA/ATAPI-8 SATA 2.x
device model CT128V4SSD2
firmware revision S5FAMM25
serial number 539C0738093100005042
cylinders 16383
heads 16
sectors/track 63
sector size logical 512, physical 512, offset 0
LBA supported 250069680 sectors
LBA48 supported 250069680 sectors
PIO supported PIO4
DMA supported WDMA2 UDMA5
media RPM non-rotating
Feature Support Enabled Value Vendor
read ahead yes yes
write cache yes yes
flush cache yes yes
overlap no
Tagged Command Queuing (TCQ) no no
Native Command Queuing (NCQ) yes 32 tags
NCQ Queue Management no
NCQ Streaming no
Receive & Send FPDMA Queued no
SMART yes yes
microcode download yes yes
security yes no
power management yes yes
advanced power management yes no 0/0x00
automatic acoustic management no no
media status notification no no
power-up in Standby no no
write-read-verify no no
unload yes yes
general purpose logging yes yes
free-fall no no
Data Set Management (DSM/TRIM) yes
DSM - max 512byte blocks yes not specified
DSM - deterministic read no
Host Protected Area (HPA) yes no 250069680/250069680
HPA - Security no
root at firewall:/home/mikej #
--mikej
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