Search results for query: raidz padding

Hello everybody, I have a zvol with a volsize of 3.91T. This zvol is attached as a data disk to a VM that works as fileserver (SAMBA/NFS). Here you have the details of df -hT from inside the VM: 2.4T used from 3.9. The zvol has volblocksize = 8K, and is on a pool with only one RAIDz-1 of four...

Parity sind die Extra-Daten die du haben willst, damit nichts verloren geht, wenn dir eine HDD ausfällt. Padding ist der Overhead den du hast, weil die Daten aus der VM ja irgendwie auf 4 HDDs aufgeteilt werden müssen und weil die Blockgrößen zwischen LBA von der HDD, Volblocksize und ashift von...

Don't know but to me it sounds more like the padding issue on RAIDZ which I have experienced as well... Need to wait until we get some clarification ;)

Ist das die maximale Kapazität? - funktioniert es uU auch mit 7 T? Beim raidZ kommt noch die blocksize des zvols ins spiel, welche zu mehr padding (und damit weniger verfügbarem platz führen kann) siehe uA folgenden artikel...

This is due to padding when using small volblocksize with raidz. See https://www.reddit.com/r/zfs/comments/b6dm4y/raidz2_used_size_double_logical_size_in_proxmox_53/?utm_source=amp&utm_medium=&utm_content=post_body for example. Try using 16k volblocksize (or whatever best value for your raidz...

4k NTFS ZVOL on RAID10 2x2Disk (4k), witch volblocksize: 8k or 16k option is better?

Thank you! Well, that's the case, I guess. root@ftp:~# zfs list -o name,used,lused,refer,ratio NAME USED LUSED REFER RATIO rpool 7.04T 5.30T 139K 1.00x rpool/ROOT 1.60G 2.59G 128K 1.87x rpool/ROOT/pve-1 1.60G...

On RAIDZ, depending on the volblocksize, you can have more used disk space than logical space, du to padding. See https://www.mail-archive.com/freebsd-virtualization@freebsd.org/msg05685.html for example Check with zfs list -o name,used,lused,refer,ratio to have a better picture of the space...

{4k} will need to be split on all disks data from your pool. But if you have let say 3x HDD raidz, then 4k will be split in 2 stripe(2k and 2k) any each will be landing on 2 HDD(2k/HDD). But your disk use 4k, so it will be write 4k insted of 2k(2k of data, ant the rest of 2k with padding). So...

You must know that zfs is a cow(copy on write) system. For this reason when you try to modify a file, there is no modification of any previous data that is all ready on pool. Insted you will have new data blocks with only new data. This is very usefull because when you make a new zfs snaphot...

That's very interesting... but the problem only affects RAIDZ2? So if I use a 4 disk RAIDZ, 8k is fine? Or should I set the volblocksize 16k as well?

The problem is facing you is that you run a cow (btrfs) over another cow (zfs). Also the 8k zvol sector size. This could be amplified if you use many small files that are very often modified. And maybe your partition inside this zvol are missaligned ?! By the way, when you create a zvol...