Re: [dm-crypt] LUKS - SSD trim

From: Felix Blanke <felixblanke@gmail.com>
To: dm-crypt@saout.de
Subject: Re: [dm-crypt] LUKS - SSD trim
Date: Thu, 22 Apr 2010 22:12:37 +0200	[thread overview]
Message-ID: <20100422221237.477736d1@gmail.com> (raw)
In-Reply-To: <4BD00C01.7050603@aktivix.org>

Hi,

first of all thank you guys a lot for helping me! 

I hope it is ok if I write one more question about those things:

I aligned the partition (which was allready fine) and the luks part to
the same value.

scooter ~ # fdisk -l /dev/sdb

Disk /dev/sdb: 160.0 GB, 160041885696 bytes
224 heads, 56 sectors/track, 24918 cylinders
Units = cylinders of 12544 * 512 = 6422528 bytes
Disk identifier: 0x5328d0af

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1          34      213220   83  Linux
/dev/sdb2              35         704     4202240   82  Linux swap /
   Solaris /dev/sdb3             705       13244    78650880   83  Linux
/dev/sdb4           13245       24918    73219328   83  Linux

scooter ~ # cryptsetup luksDump /dev/sdb4
...
Payload offset: 12544
...

The filesystem on top is btrfs. I didn't find any information about the
align thing and btrfs. I dont know mutch about align and those stuff :/

The problem is:

scooter ~ # hdparm -tT /dev/sdb3

/dev/sdb3:
 Timing cached reads:   18686 MB in  2.00 seconds = 9354.32 MB/sec
 Timing buffered disk reads:  758 MB in  3.00 seconds = 252.61 MB/sec

scooter ~ # hdparm -tT /dev/mapper/ssd 

/dev/mapper/ssd:
 Timing cached reads:   17432 MB in  2.00 seconds = 8725.18 MB/sec
 Timing buffered disk reads:  158 MB in  3.02 seconds =  52.36 MB/sec

The first value is perfect, then second one really sucks.
Obv. /dev/mapper/ssd is the decrypted /dev/sdb3

Any idea about that?

Regards,
Felix

Am Thu, 22 Apr 2010 09:42:41 +0100
schrieb mark <mark@aktivix.org>:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 22/04/10 03:17, Arno Wagner wrote:
> > You can image it to a file on a conventional disk and
> > image it back, e.g. wioth dd_rescue. That should
> > also fix things, at least for a while.
> 
> I guess it might help to check that your partitions are aligned to the
> erase blocks on the SSD, before you restore the image of your brtfs.
> Look here
> http://www.saout.de/pipermail/dm-crypt/2010-February/000584.html
> 
> Cheers,
> Mark
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