Hi,
Hernan Freschi wrote:
Hi, thanks for answering,
How large is your ARC / your main memory?
Probably too small to hold all metadata (1/1000 of the data amount).
=> metadata has to be read again and again
Main memory is 8GB. ARC (according to arcstat.pl) usually stays at 5-7GB
A recordsize smaller than 128k increases the problem.
recordsize is default, 128k
Its a data volume, perhaps raidz or raidz2 and you are using an older ZPOOL
version?
It's raidz, pool version is 22
Reading is done for the whole raid stripe when you are reading a block.
=> the whole raidz stripe has the attributes of a single disk (see Roch's
blog).
The number of files is not specified.
some 20 files deleted, each about 4GB in size
Updating the dedup table needs random access of the table.
dedup was enabled at some point, but I disabled it long ago. Does it
still matter? Should I copy all these files again (or zfs send) to
un-dedup those blocks?
When you are writing to a file and currently dedup is enabled, then the
Data is entered into the dedup table of the pool.
(There is one dedup table per pool not per zfs).
Switching off the dedup does not change this data.
After switching off dedup, he dedup table is used until this file is
deleted or overwritten.
Deleting or overwriting then accesses the dedup table and corrects the
reference count.
Therefore you will see effects of the dedup table long after switching
dedup off,
as long you wrote the file during a time dedup was switched on.
~ 60 reads per second is normal for a sata disk with 7200 RPM.
shouldnt ~60 reads per second at about 128k (not counting prefetch) be
about 7MB/s, instead of the 144kbps (!) I'm getting?
ZFS can use smaller blocks, metadata is usually compressed and in the
dedup table
it is possible, that a dedup block compresses well, when only one slot
on a block is used,
then a 128k block (logical) can be stored in a 2k physical block.
Regards,
Ulrich
--
Ulrich Graef / Sales Consultant / Hardware Presales / Phone: + 49 6103 752 359
ORACLE Deutschland B.V. & Co. KG / Amperestr. 6 / 63225 Langen
http://www.oracle.com
ORACLE Deutschland B.V. & Co. KG
Hauptverwaltung: Riesstr. 25, D-80992 Muenchen
Registergericht: Amtsgericht Muenchen, HRA 95603
Komplementaerin: ORACLE Deutschland Verwaltung B.V.
Rijnzathe 6, 3454PV De Meern, Niederlande
Handelsregister der Handelskammer Midden-Niederlande, Nr. 30143697
Geschaeftsfuehrer: Juergen Kunz, Marcel van de Molen, Alexander van der Ven
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
