Why does the # of blocks change for a file on a ZFS filesystem?

Login or Register to Ask a Question and Join Our Community

Why does the # of blocks change for a file on a ZFS filesystem?

Tags

solaris, unresolved, unresolved for months, unresolved for weeks

Login to Discuss or Reply to this Discussion in Our Community

Operating Systems Solaris Why does the # of blocks change for a file on a ZFS filesystem?

02-02-2009

Registered User

19, 0

Join Date: Dec 2008

Last Activity: 20 February 2009, 2:14 AM EST

Posts: 19

Thanks Given: 0

Thanked 0 Times in 0 Posts

Why does the # of blocks change for a file on a ZFS filesystem?

I created a zpool and zfs filesystem in OpenSolaris. I made two NFS mount points:

> zpool history

History for 'raidpool':
2009-01-15.17:12:48 zpool create -f raidpool raidz1 c4t1d0 c4t2d0 c4t3d0 c4t4d0 c4t5d0
2009-01-15.17:15:54 zfs create -o mountpoint=/vol01 -o sharenfs=on -o canmount=on raidpool/vol01
2009-01-15.17:20:13 zfs create -o mountpoint=/vol02 -o sharenfs=on -o canmount=on -o compression=lzjb raidpool/vol02

I did not make the mountpoints (vol01 and vol02) into volumes. I know you can set default blocksizes when you create volumes but you cannot make them exportable NFS exports.

I am assuming that vol01 and vol02 are variable blocksizes because I did not explicitly specify a blocksize. Thus, my assumption is that ZFS would use a blocksize that is the the smallest power of 2 and the smallest blocksize is 512 bytes.

I use the stat command to check the filesize, the blocksize, and the # of blocks.

I created a file that is exactly 512 bytes in size on /vol01 (the one without the LZ compression)

I do the following stat command:
stat --printf "%n %b %B %s %o\n" *

The %b is the number of blocks used.

The number of blocks changes after a few minutes after the file is created:

# stat --printf "%n %b %B %s %o\n" *
file.0 3 512 3 4096
file.512 1 512 512 4096
# stat --printf "%n %b %B %s %o\n" *
file.0 3 512 3 4096
file.512 1 512 512 4096
# stat --printf "%n %b %B %s %o\n" *
file.0 3 512 3 4096
file.512 3 512 512 4096

Why does the # of blocks change after a few minutes? And why are we using 3 blocks when the file is only 512 bytes in size (in other words, only 1 block is needed)???

sqa777

View Public Profile for sqa777

Find all posts by sqa777

Login or Register to Ask a Question

Previous Thread | Next Thread

7 More Discussions You Might Find Interesting

1. UNIX for Beginners Questions & Answers

How to finish expanding a zfs filesystem?

I have a esxi 6.7 server running a Solaris 10 x86 vm (actually a bunch of them). The VM uses zfs for the pools (of course). I expand the underlying ESX logical disk, for example from 50GB to 100gb, then I set autoexpand=on <pool> that belongs to the esx logical disk. what am i missing to...

2. Solaris

Extend zfs storage filesystem

Hello, Need to ask the question regarding extending the zfs storage file system. currently after using the command, df -kh u01-data-pool/data 600G 552 48G 93% /data /data are only 48 gb remaining and it has occupied 93% for total storage. zpool u01-data-pool has more then 200 gb...

3. Solaris

ZFS Filesystem

Hi, Recently we have new server T5 Oracle. We set up it for our database. For out database files we set one zfs filesystem. When i use iostat -xc the output as below. As you see the value for vdc4 is quite high. extended device statistics cpu device ...

4. Shell Programming and Scripting

how to split this file into blocks and then send these blocks as input to the tool called Yices?

Hello, I have a file like this: FILE.TXT: (define argc :: int) (assert ( > argc 1)) (assert ( = argc 1)) <check> # (define c :: float) (assert ( > c 0)) (assert ( = c 0)) <check> # now, i want to separate each block('#' is the delimeter), make them separate files, and then send them as...

5. Filesystems, Disks and Memory

Howto Convert a filesystem from Veritas to ZFS?

Hi Folks, Looking for info here more than any actual HowTo, does anyone know if there is an actual way of converting a Veritas or UFS filesystem to ZFS leaving the resident data intact. All that I have been able to find, including the commercial products seem to require the FS backed up from...

6. Solaris

Mount old zfs filesystem

Hey all, I have a machine with 16 drive slots. Two of the drives have a ZFS mirror of the operating system, the other 14 contain the storage raidz. So, after installing Opensolaris on the OS drives, how can I remount the storage raid? TIA

7. Solaris

How do I export a zfs filesystem that I created?

I created a zpool and two ZFS volumes in OpenSolaris. I would like both ZFS volumes to be exportable. However, I don't know how to set that up. These are the steps I did: 1) Create the zpool using raidz1 across five disks. I have six disks and created a zpool across 5 of them. c4t0d0...

Login or Register to Ask a Question