OS/2, eCS & ArcaOS - Technical > Setup & Installation

SSD partition miss aligned.

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Dariusz Piatkowski:
Remy, everyone...


--- Quote from: Remy on February 03, 2022, 05:38:54 am ---
--- Quote from: Dave Yeo on February 03, 2022, 12:42:26 am ---It's the usual problem, need to do all partitioning with OS/2 aware tools, and do some math to have the 4k sector partitioning, basically JFS 4k sectors need to align with the SSD's 4k sectors...
--- End quote ---
...
Before, I had H255 and S63  (of course, sector size always left at default 512...)
But this resulted to unaligned partition while Dfsee found it aligned (ok for HDD) but it isn't for SSD.
...
--- End quote ---

Dave brought up an important point, at least from a performance perspective: the alignment of hardware and software implementation.

So 4k sector size for SSD, and unless you MUST pick something different from JFS IFS perspective, you would want the same matching 4k JFS blocksize (see format's /BS parameter).

The HELP page for our format specifically states:


--- Quote ---...The block size specified must not be smaller than the sector size of the device....

--- End quote ---

...however what I do not know (having never tried it myself) is what would happen if you do try a JFS blocksize <4K?

Anyways, re: the above sync, my expectation would be that this would assure a minimal overhead for all processing.

Dave Yeo:
I experimented with small block sizes years back. Mostly found that performance decreased with a smaller block size, which from what I read was expected unless you deal with mostly small files. Also lose Linux compatibility as they never bothered to implement small blocks.
Another option for small block size is HPFS, which uses 512k sectors with a minimum file size or 2 sectors. Also get away from the journal and all the wear that puts on the SSD.
Linux also allows disabling atime (access time) which updates the files timestamp when simply looking at a file causing a slight performance hit and more writing. Use the properties notebook-->files to see the various times or use stat,

--- Code: ---W:\>stat config.sys
  File: config.sys
  Size: 8739            Blocks: 18         IO Block: 49152  regular file
Device: 5657h/22103d    Inode: 14964592257604998832  Links: 1
Access: (0666/-rw-rw-rw-)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2022-02-05 08:49:48.000000000 -0800
Modify: 2022-01-30 09:21:24.000000000 -0800
Change: 2022-01-30 09:21:24.000000000 -0800
 Birth: 2022-01-30 09:21:24.000000000 -0800

--- End code ---

Shows I looked at config.sys on the 5th.

Remy:
My last test:
I used my older and smaller SSD (240GiB)
- Added 3 partitions fat32 no name no letter under windows (first one was created with a 1MiB start offset  (ok, aligned))

Now booted into ArcaOS with AHCI /A:0 /P:1 /4   this SSD been at this adapter / port number  (/4 to use 56 sectors as it is written)
I could see my disk under DFSEE and the 1MiB free offet before the first partition
I opened LVM, LVM could see it with the good size value
I tried to set names and letter but LVM replied unable to update the disk ...  (The disk is seen under LVM but in fact unusable from under LVM)
Like this, partitions unusable
I deleted partition and created them using LVM (simple), partitions where created.
I check under DFSEE and none are aligned (system CCC 255 63 and logical CCC 64 32)
From my test, I do not understand what /4 parameter on AHCI  is realy supposed to do.
In all cases I tested, i never could have aligned partition on SSD usable by ArcaOS and airboot requires 63 sectors to allow its installation.

From my point of view, this is major issue to be resolved because it has lifetime issue on SSD which are more and more used in replacement of HDD.
(New SSD have a big write possibilities but when you do many write operation a day [several GiB], it is good to preserve its lifetime with correct SSD usage - and been use it correclty under linux for fstrim is welcome too to gain speed again when it drop down)

If someone is able to find the solution to correct this, I'm interested

Regards
Rémy         

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