Status of SSDs under Fedora ?

John Austin ja at jaa.org.uk
Tue Jun 15 10:22:29 UTC 2010


On Mon, 2010-06-14 at 14:24 -0500, Michael Cronenworth wrote:
> John Austin wrote:
> > 3. Does setting the "discard" option do everything that is required to enable
> > TRIM to do its job with no further action?
> 
> Yes.
> 
> >
> > 4. Is it safe to use the "discard" option yet?
> 
> I am using ext4 on /boot. btrfs on /. No issues with /boot or /. There 
> were a few mailings[1] about performance issues with btrfs, but I have 
> not seen any negative effects in normal desktop usage.
> 
> [1] http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg03443.html

Hi All

Many thanks for the replies

I think I have taken them all on board
However I have failed to properly sort out the "hotplug" options so
far ! Still working on it.

My SSD (which dangles on an eSATAp cable) is used in two modes

1. As a "fixed" F13 test disk (ext4 partition) (Mode 1)
2. As a "hot-pluggable" backup disk (Mode 2)

It has 3 partitions as follows (to achieve alignment)
(fdisk)
Disk /dev/sdb: 128.0 GB, 128035676160 bytes
224 heads, 56 sectors/track, 19935 cylinders
Units = cylinders of 12544 * 512 = 6422528 bytes
Disk identifier: 0xfc656088
   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               5          20      100352   83  Linux
/dev/sdb2              21        6400    40015360   83  Linux
/dev/sdb3            6401       19932    84872704   83  Linux
--------------------------
(parted) unit cyl
(parted)
p                                                                
Model: ATA C300-CTFDDAC128M (scsi)
Disk /dev/sdb: 19935cyl
Sector size (logical/physical): 512B/512B
BIOS cylinder,head,sector geometry: 19935,224,56.  Each cylinder is
6423kB.
Partition Table: msdos
Number  Start    End       Size      Type     File system  Flags
 1      4cyl     19cyl     16cyl     primary  ext3
 2      20cyl    6399cyl   6380cyl   primary  ext4
 3      6400cyl  19931cyl  13532cyl  primary  ext3
-------------------------------------------------------------
In Mode 1 the scheduler is set by a script at boot time
Effectively it does
echo noop > /sys/block/sdb/queue/scheduler
the device (sdb shown) is sorted out using blkid
-------------------------------------------------------------
In Mode 1 the noatime and discard options are set in fstab
[root at naxos ~]# cat /etc/fstab
...
UUID=f02d542f-2ad4-487f-bda2-d3135c404c78 /  ext4
defaults,noatime,discard   1 1
#############################################################
Currently in Mode 2 I have a script that has to be run as root
to set the scheduler and options as above after the SSD is plugged in.

To my knowledge I have had no problems with the discard option.

Regards

John







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