Chookiex writes:
> Hi all,
>
> I have 2 questions about ZFS.
>
> 1. I have create a snapshot in my pool1/data1, and zfs send/recv it to
> pool2/data2. but I found the USED in zfs list is different:
> NAME USED AVAIL REFER MOUNTPOINT
> pool2/data2 160G 1.44T 159G /pool2/data2
> pool1/data 176G 638G 175G /pool1/data1
>
> It keep about 30,000,000 files.
> The content of p_pool/p1 and backup/p_backup is almost same. But why is the
> size different?
>
160G for 30M files means your avg file size is 5333 Bytes.
Pick one such files just for illustration: 5333 Bytes to be
stored on raid-z2 of 5 disks (3+2). So you have to store
5333 Bytes of data onto 3 data disks. You will need a stripe
of 4 x 512B sectors on each of the 3 data disks. So that's
6K of data.
Over a single volume, you'd need 11 sectors of 512B to store
5632 Bytes.
For this avg file size you thus have either 12 or 11 sectors
to store the data, a 9% difference.
You then need to tack the extra parity blocks. For raid-z2
is a double parity scheme whereas raid-5 is single parity
(and will only survice a single disk failure).
Depending on how these parity blocks are accounted for and
your exact files size distribution, the difference you note
does not appear unwaranted.
> 2. /pool2/data2 is a RAID5 Disk Array with 8 disks, and , and /pool1/data1
> is a RAIDZ2 with 5 disks.
> The configure like this:
>
> NAME STATE READ WRITE CKSUM
> pool2 ONLINE 0 0 0
> c7t10d0 ONLINE 0 0 0
>
>
> NAME STATE READ WRITE CKSUM
> pool1 ONLINE 0 0 0
> raidz2 ONLINE 0 0 0
> c3t2d0 ONLINE 0 0 0
> c3t1d0 ONLINE 0 0 0
> c3t3d0 ONLINE 0 0 0
> c3t4d0 ONLINE 0 0 0
> c3t5d0 ONLINE 0 0 0
>
> We found that pool1 is more slow than pool2, even with the same number of
> disks.
> So, which is better between RAID5 + ZFS and RAIDZ + ZFS?
>
Uncached RAID-5 random read is expected to deliver more
total random read IOPS than uncached Raid-Z.
The downside if using single raid-5 volume is that if a
checksum error is ever detected by ZFS, ZFS report the error
but will not be able to correct data blocks (metadata blocks
are stored redundantly and will be corrected).
-r
>
> <html><head><style type="text/css"><!-- DIV {margin:0px;}
> --></style></head><body><div style="font-family:"Times New Roman", "new
> york", "times", serif;font-size:12pt"><DIV>Hi all,<BR></DIV><DIV>I have 2
> questions about ZFS.</DIV><DIV><BR></DIV><DIV>1. I have create a snapshot in
> my pool1/data1, and zfs send/recv it to pool2/data2. but I found the USED in
> zfs list is different:</DIV><DIV>NAME USED AVAIL
> REFER MOUNTPOINT</DIV><DIV> pool2/data2 160G 1.44T 159G
> /pool2/data2</DIV><DIV> pool1/data 176G 638G 175G
> /pool1/data1 </DIV><DIV><BR></DIV><DIV>It keep about 30,000,000
> files.</DIV><DIV>The content of p_pool/p1 and backup/p_backup is almost
> same. But why is the size different?</DIV><DIV><BR></DIV><DIV>2.
> /pool2/data2 is a RAID5 Disk Array with 8 disks, and , and /pool1/data1 is a
> RAIDZ2 with 5 disks.</DIV><DIV>The configure like this:</DIV><DIV><BR>
> NAME STATE
> READ WRITE CKSUM<BR> pool2 ONLINE 0 0 0<BR>
> c7t10d0 ONLINE 0 0 0<BR></DIV><DIV><BR> NAME
> STATE READ WRITE CKSUM<BR> pool1 ONLINE 0
> 0 0<BR> raidz2 ONLINE 0 0 0<BR>
> c3t2d0 ONLINE 0 0 0<BR> c3t1d0 ONLINE 0
> 0 0<BR> c3t3d0 ONLINE 0 0 0<BR>
> c3t4d0 ONLINE 0 0 0<BR> c3t5d0 ONLINE 0
> 0 0</DIV><DIV><BR></DIV><DIV>We found that pool1 is more slow than
> pool2, even with the same number of disks.</DIV><DIV>So, which is better
> between RAID5 + ZFS and RAIDZ +
> ZFS?</DIV><DIV><BR><BR></DIV><DIV><BR></DIV></div><br>
>
>
>
> </body></html>
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss@opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
