Re: [zfs-discuss] ZFS + DB + default blocksize
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Louwtjie Burger wrote: On 11/8/07, Richard Elling [EMAIL PROTECTED] wrote: Potentially, depending on the write part of the workload, the system may read 128 kBytes to get a 16 kByte block. This is not efficient and may be noticeable as a performance degradation. Hi Richard. The amount of time it takes to position the drive to get to the start of the 16K block takes longer than the time it takes to read the extra 112 KB ... depending where on the platter this is one could calculate it. Worse yet, if your zfs blocksize is 128KB and your database worksize is 16Kbytes, ZFS would load 128Kbytes, update 16 kbytes inside there and write out 128 kbytes to the disk. If both blocksizes are equal, you don't need the read part. That is a huge win. - -- Jesus Cea Avion _/_/ _/_/_/_/_/_/ [EMAIL PROTECTED] http://www.argo.es/~jcea/ _/_/_/_/ _/_/_/_/ _/_/ jabber / xmpp:[EMAIL PROTECTED] _/_/_/_/ _/_/_/_/_/ _/_/ _/_/_/_/ _/_/ _/_/ Things are not so easy _/_/ _/_/_/_/ _/_/_/_/ _/_/ My name is Dump, Core Dump _/_/_/_/_/_/ _/_/ _/_/ El amor es poner tu felicidad en la felicidad de otro - Leibniz -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iQCVAwUBRztjCplgi5GaxT1NAQIxHAP/VH142N+TAfFpZweli6FofC2r0lreB9zx yvhqZa6i4UHpMKHHODIlLL76iMc10rtT0o0of/Tlm3Ohz/ZDjZ4Emh13zLx4+EBk JizrFKSBfnEa3KVJ4j2rTRRDsqCelw9YTmfUnd+eUk3hw2GNwpocVDK3QVkS1xWM vuUdxUAdnZc= =UlDy -END PGP SIGNATURE- ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS + DB + default blocksize
Louwtjie Burger writes: Hi What is the impact of not aligning the DB blocksize (16K) with ZFS, especially when it comes to random reads on single HW RAID LUN. How would one go about measuring the impact (if any) on the workload? The DB will have a bigger in memory footprint as you will need to keep the ZFS record for the lifespan of the DB block. This probably means you want to partition memory between DB cache/ZFS ARC cache according to the ratio of DB blocksize/ZFS recordize. Then I imagine you have multiple spindles associated with the lun. If you're lun is capable of 2000 IOPS over a 200MB/sec data channel then during 1 second at full speed : 2000 IOPS * 16K = 32MB of data transfer, and this fits in the channel capability. But using say a ZFS blocks of 128K then 2000 IOPS * 128K = 256MB, which overload the channel. So in this example the data channel would saturate first preventing you from reaching those 2000 IOPS. But with enough memory and data channel throughput then it's a good idea to keep the ZFS recordize large. -r Thank you ___ 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
Re: [zfs-discuss] ZFS + DB + default blocksize
Yes. Blocks are compressed individually, so a smaller block size will (on average) lead to less compression. (Assuming that your data is compressible at all, that is.) This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
